VIRUSES
An outbreak of influenza A (H1N1) virus in a remote Aboriginal community post-pandemic: implications for pandemic planning and health service policy Philippa J. Chidgzey,1,2 Stephanie Davis,2 Peta Williams,1 Carole Reeve1
A
boriginal people were disproportionately affected in the influenza pandemic of 2009.1 The pandemic had a less severe impact on the general population than originally anticipated;2 however, Aboriginal people were more likely to require admission to hospital and more likely to die from influenza than non-Aboriginal Australians.1,3,4 In addition, the 2009 pandemic confirmed that Aboriginal people experience the complications of the influenza virus, whether pandemic or seasonal strains, more often than the non-Aboriginal Australian population.1,4,5 Reasons for these disparities are multifactorial, including high prevalence of chronic diseases, high pregnancy rates and socioeconomic factors such as reduced access to health care and barriers to health-seeking behaviour.1,5,6 Since causing the pandemic in 2009, the influenza A(H1N1) virus (abbreviated as A(H1N1)pdm09)2,7 has been circulating in the Australian population and is now considered a seasonal strain. The strain has been incorporated into the trivalent seasonal influenza vaccine since 2010.8 The general population is no longer considered to be A(H1N1)pdm09 naïve due to previous exposure or vaccination.9 Thus, the strain is not expected to cause greater morbidity or mortality than other seasonal strains. As currently available seasonal influenza vaccines confer protection for about a year, annual vaccination is required for ongoing protection.10
Abstract Objective: To describe a 2013 outbreak of pandemic influenza A (H1N1) virus in a remote Western Australian Aboriginal community; inform outbreak prevention and control measures and discuss the community susceptibility to H1N1, three years after the A(H1N1)pdm09 pandemic. Methods: Records at the local clinic were used to classify cases as ‘confirmed’ (laboratory test positive for H1N1 or temperature >38°C with cough and/or sore throat) or ‘probable’ (selfreported fever with cough and/or sore throat). Additional data were collected from medical records and public health databases. Results: A total of 108 individuals met case definitions. Clinical attack rate was 23%. Children under five years of age had the highest age-specific attack rate (545 per 1,000 population). Thirty cases (28%) experienced complications with six (5.6%) requiring aero-evacuation. Only 7% of the community had received H1N1-containing vaccine during the previous year. No H1N1 cases from the community were previously reported. Conclusions: This is the first description of the effects of a novel influenza strain on a remote Australian Aboriginal community. Isolation and low vaccination are likely explanations for the apparent naivety to H1N1. Implications: There may be other remote communities at risk of H1N1. High attack and complication rates confirm that Aboriginal Australians should be prioritised in pandemic planning. Key words: outbreak, influenza, Aboriginal, remote, susceptibility Globally, Aboriginal populations are at higher risk of increased exposure, clinical infection, complications and consequences of influenza. Socioeconomic and cultural circumstances often determine that large families live together.11,12 Overcrowding leads to increased transmission of the influenza virus,13,14 resulting in high influenza attack rates in Indigenous populations internationally.11,15,16 Aboriginal people in Australia also are known to be an at-risk group for influenza;2,17 however, less is known about the natural
history of the influenza virus within remote Aboriginal communities. In March 2013, a paediatrician reported a suspected outbreak of influenza-like illness (ILI) in a remote Aboriginal community in north-west Western Australia to the regional population health unit. An investigation was conducted by the regional population health unit with the following objectives: to describe and control the outbreak; to determine why the community had remained vulnerable to A(H1N1)pdm09 more than three years after
1. Kimberley Population Health Unit, Western Australia Country Health Service, WA 2. National Centre for Epidemiology and Population Health, ANU College of Medicine and Health Sciences, Australian National University, ACT Correspondence to: Dr Philippa J. Chidgzey, Kimberley Population Health Unit, Western Australia Country Health Service, PO Box 525, Broome, WA 6725; e-mail: [email protected] Submitted: May 2014; Revision requested: June 2014; Accepted: August 2014 The authors have stated they have no conflict of interest. Aust NZ J Public Health. 2015; 39:15-20; doi: 10.1111/1753-6405.12295
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the 2009 pandemic; and to inform prevention and control measures for future influenza outbreaks in remote Aboriginal communities.
Methods
cardiovascular complications, neurological complications, encephalitis, Reye syndrome, renal dysfunction, liver dysfunction, bone marrow dysfunction or other documented complication.10,23,24
Outbreak setting
Epidemiological investigation
The remote community has no road access for most of the year due to tropical rains and is accessed by aeroplane or boat. The population size fluctuates and is estimated at 400 to 500 residents.18 There is a relatively young age distribution, as is common in Aboriginal communities.6,19 Housing is limited and overcrowding is common.20 The community is serviced by a nurse-led remote area clinic with a visiting doctor service two days per week.
The clinic log, which codes every patient presentation according to clinical signs and symptoms, was reviewed for the dates from 25 February 2013 to 8 April 2013. Electronic and paper records were then reviewed for all patients with presentations coded as ILI to determine whether they met the outbreak case definition and, if so, to collect further details about each case including demographic details, risk factors for complications, vaccination status, symptoms, complications, treatment and tests performed. Individuals were excluded from all counts, figures and analysis if the medical record could not be located. Data were entered and analysed using Epi Info 7.25
Case definitions Outbreak case definitions were modified from the Communicable Diseases Network Australia (CDNA) influenza guidelines for public health units.17 A confirmed case was defined as a community resident and either laboratory confirmed with laboratory test positive for H1N1 or clinically confirmed with measured temperature of >38°C at time of clinic presentation with cough and/or sore throat, with onset from 25 February 2013 to 8 April 2013. A probable case was defined as a community resident with self-reported fever with cough and/or sore throat with onset between 25 February 2013 to 8 April 2013.17 Laboratory testing was undertaken via dry throat swab polymerase chain reaction (PCR) assay of influenza A virus H1N109 RNA.21 Dry swabs were transported by aeroplane to the public health reference laboratory in Western Australia for testing. Other viruses tested for in the respiratory panel were Adenovirus, Enterovirus/ Rhinovirus, Human Metapneumovirus, Influenza B virus, Parainfluenza 1,2 and 3 and Respiratory Syncytial Virus.21 Both probable and confirmed ILI cases were included in the numerator. Risk factors for severe influenza were taken from the CDNA influenza guidelines for public health units.17 Severe influenza was considered to be the requirement for hospitalisation, admission to intensive care units or death.22,23 A complication was recorded if there was clinical documentation of any of the following features: primary or secondary bacterial pneumonia, bronchitis, croup, acute otitis media,
16
Overall and age specific attack rates were calculated using 2011 census data.18 To examine community susceptibility to H1N1, the Western Australian Notifiable Infectious Diseases Database (WANIDD)26 was reviewed for prior cases of A(H1N1)pdm09 in the community. Case clinic notes were also reviewed for previous presentations of ILI. Community immunisation coverage from 2009 to 2013 was determined via review of the public health immunisation database that collects immunisation data from both adults and children in the Kimberley (HCare) and the clinic electronic medical record system.
Results The outbreak was first reported by clinical staff on 12 March 2013 as a cluster of eight children presenting with ILI and haematuria on urine dipstick. Initial reports considered an arbovirus as a possible cause; however, six specimens tested positive for influenza A(H1N1)pdm09 virus on Saturday 16 March 2013. The outbreak investigation and response followed. According to the clinic log, 129 patients presented with ILI during the outbreak time period. Of these, medical records could be located for 108 patients, all of whom met the outbreak case definitions. This gave a clinical attack rate of 23%. Seventy individuals (65%) met the definition for a confirmed case while 38 (35%) met the definition for a probable case. Thirty cases (27%) had swab samples sent for testing. Influenza A(H1N1)pdm09 virus was detected in 27 of these (90%). Figure 1 shows the epidemic curve. The case with the earliest date of illness onset did not report any travel outside of the community during the previous two weeks (27/2/2013); however, the case with the second earliest date of illness onset (28/3/2013) had travelled throughout the Kimberley region by bus five days prior to symptom onset.
Characteristics of cases The median age of cases was 11.5 years ranging from zero to 80 years. The majority of cases were children with 23 cases aged
Figure 1: Epidemic curve of the remote community outbreak by outbreak case definition.
* Confirmed cases include both laboratory confirmed and clinically confirmed cases.
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five to nine years (20%). Figure 2 shows the age-specific attack rates. Those aged zero to four years had the highest age-specific rates. Males made up 33% of cases (n=36) and 67% of cases were female (n=72). When examined by risk factors for severe influenza,17,22 10 cases (9%) were under two years of age and 104 (95%) were Aboriginal people. Eleven cases (10%) had a record of smoking, 17 (16%) had documented chronic lung disease (chronic obstructive pulmonary disease or asthma), nine (8%) had congenital or chronic heart disease, 10 (9%) had chronic renal disease, 15 (14%) had type 2 diabetes mellitus and one case had a known pregnancy. Table 1 shows the proportions of cases with symptoms, signs and complications as documented in medical records. Proportions of laboratory confirmed cases with risk factors for severe influenza were similar to the overall case group (results not shown). Six cases (5.6%) were flown out of community for hospitalisation. Reasons for these aeromedical evacuations were secondary bacterial pneumonia, febrile convulsion, dehydration and croup. No cases of encephalitis, Reyes syndrome, cardiovascular complications or multi-organ complications were reported. There were no documented fatalities.
On initiation of the investigation, alerts were sent by the population health unit to the community clinic, regional hospital doctors
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Three findings deserve particular mention. First, the clinical attack rate of 23% was higher
* Confirmed cases include both laboratory confirmed and clinically confirmed cases.
Table 1: Number and proportions of symptoms, signs and outcomes recorded in medical notes. Factor
Control measures
To our knowledge, this is the first described outbreak of influenza A(H1N1)pdm09 virus in a remote Australian Aboriginal community to be systematically investigated. The outbreak had a large impact on a community already burdened by a high prevalence of underlying medical conditions.28 The high attack and complication rates suggest that the community was most likely H1N1 naïve due to low vaccination coverage and lack of previous exposure to the A(H1N1)pdm09 virus as a result of isolation.
Figure 2: Age specific attack rates per 1000 population by outbreak case definition.
Number and proportion of cases with symptom/ sign or outcome
Immunity or previous exposure Prior to the outbreak, there had never been a case of A(H1N1)pdm09 from the community recorded on WANIDD. In addition, one current outbreak case had presented during the influenza pandemic of 2009 and was laboratory test negative for A(H1N1)pdm09 virus and other influenza strains at that time. As at 20 March 2013, the annual community influenza vaccination coverage rate was estimated at 7%. Of the identified cases in this outbreak, 11 were documented as having been vaccinated in 2012 with the seasonal trivalent influenza vaccine. Additionally, 32 cases (30%) received single valent A(H1N1) pdm09-containing Panvax® in 2009/2010. Overall, 46 cases (43%) had ever received either a single valent or trivalent A(H1N1) pdm09-containing influenza vaccine since 2009.
Discussion
and Aboriginal Medical Services advising of the current outbreak, influenza treatment guidelines,17 vaccination recommendations10 and information for patients regarding control measures including social distancing and hand washing.17,27 Lay language alerts were displayed outside the community clinic, shop and school. Copies were also provided to the community council for distribution to community residents. Over the following days, supplies of vaccinations and Oseltamivir for specific cases17 were dispatched to the community. Two cases received treatment with Oseltamivir. Clinic nurses and a team from regional disease control provided 160 influenza vaccinations within 2.5 days.
Total number of cases
Number and proportion of laboratory confirmed cases with symptom/ sign or outcome
Number and proportion of cases aged less than 5 years
Number and proportion of cases aged 5-12 years
Number and proportion of cases aged greater than 12 years
108
27 (25%)
24 (22%)
32 (30%)
52 (48%)
Temperature >38° C
63 (59%)
20 (74%)
16 (25%)
25 (40%)
22 (35%)
Cough
88 (82%)
20 (74%)
21 (24%)
25 (28%)
42 (48%)
Sore Throat
48 (44%)
13 (48%)
5 (10%)
13 (27%)
30 (63%)
Headachea
28 (26%)
8 (30%)
1(4%)
8 (29%)
19 (68%)
Gastrointestinal upset
17 (16%)
8 (30%)
7 (41%)
3 (18%)
7 (41%)
8 (7%)
5 (19%)
1 (13%)
4 (50%)
3 (38%)
Symptoms/Signs
Haematuria on urine dipstick
a
Outcomes Hospitaliseda
6 (6%)
5 (19%)
4 (67%)
1 (17%)
1 (17%)
Complication
31 (29%)
11 (41%)
11 (36%)
10 (32%)
10 (32%)
8 (7%)
4 (15%)
2 (25%)
0
6 (75%)
Secondary Bacterial Pneumonia Bronchitis
7 (7%)
0
0
4 (57%)
3 (43%)
Acute Otitis Media
5 (5%)
3 (11%)
3 (60%)
1 (20%)
1 (20%)
Croup
2 (2%)
0
2 (100%)
0
0
Neurological complicationsb
2 (2%)
2(7%)
1 (50%)
1 (50%)
0
Complication-other
7 (6%)
2 (7%)
3 (43%)
4 (57%)
0
a: Age-specific proportions do not equate to 100% due to rounding b: seizure or hallucinations
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than findings from other pandemic H1N1 publications in the general population.7,29 Secondly, female cases predominated in the adult age group, potentially a reflection of differences in health seeking behaviour between genders, and/or differences in child-care responsibilities. Thirdly, as reported elsewhere, there were high age-specific attack rates in the younger age groups.7,11,29,30 While the epidemiology of A(H1N1) pdm09 has been well described in many populations,22,30-32 data regarding the effect of H1N1 on remote Australian Aboriginal populations have remained scarce.1 To our knowledge there are no other published reports of a pandemic influenza outbreak in a remote Australian community for comparison. However, our findings are similar to a report from a remote Indigenous community in Canada that showed a similar attack rate with little difference in characteristics between laboratory confirmed and probable cases. Young children were disproportionately affected, as was the case in this outbreak.15 A feature of this outbreak that has not been described in other A(H1N1)pdm09 reports1,31,32 was the presence of microscopic haematuria on urine dipstick in eight children. Haematuria has not previously been recognised as a complication of seasonal influenza either.23 However, the significance of this finding in the setting of febrile illness is unclear. First, the haematuria was found only on urine dipstick and not laboratory confirmed. Second, not all cases were tested for haematuria and the prevalence of haematuria in the community is not available. While there have been limited studies on the prevalence of haematuria in Aboriginal children living in remote Australia,33 anecdotally, incidental haematuria is a not infrequent finding in both well and febrile children. The community was likely to have been susceptible to this outbreak for several reasons, one of these being because the annual vaccination coverage was low. The CDNA recommended the target of 50% coverage to contain community transmission of H1N1 in the pandemic year.17 The calculated 7% coverage rate estimated for this community fell well short of this target. Recently published data for comparison of adult coverage rates in other remote communities is scarce. However, a Communicable Disease Intelligence publication reported vaccination coverage in
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other remote Western Australian Aboriginal populations in 2005, with 65% of remote Aboriginal people aged 50-64 years and 20% of Aboriginal people aged 15-49 years receiving influenza vaccine within the previous 12 months.34 A 2013 updated report did not include influenza vaccination coverage35 for a more recent comparison. Another contributing factor to the community’s vulnerability to an outbreak was the apparent naivety to A(H1N1)pdm09 virus. The primary circulating influenza strain across the Kimberley region in 2009 was pandemic H1N1.26 Thus, it was originally assumed that most of the regional population would have been exposed to the circulating virus at some point. By contrast, there had never been a notification captured by WANIDD of A(H1N1)pdm09 virus originating from this particular community prior to this outbreak.26 Further, senior community members reported to the investigation team that no “swine flu” occurred in the community during the pandemic influenza year. Additionally, ongoing research in influenza A(H7N9) has suggested that Aboriginal populations may lack genetic cross-protective immunity against pandemic influenza strains.36 According to WANIDD,26 there were isolated A(H1N1)pdm09 cases in two other communities in March 2013 with no further transmission recorded in either area. In addition, A(H1N1)pdm09 virus was introduced into another remote community (community B) at the same time the outbreak was progressing. Transmission ceased in community B at six cases. Community B had both notified cases of previous A(H1N1) pdm09 virus and high community vaccination levels against influenza, supporting our conclusion that the H1N1 naivety of the community where the outbreak occurred was central to the epidemic.
Study limitations There are a number of limitations to this study. In this setting, defining an accurate denominator population is always challenging given the high mobility of remote Aboriginal people.37 However, we consider the Australian Bureau of Statistics (ABS) population estimate to be reasonably accurate as this was very similar to the population figure held by the clinic (unpublished data). Not all cases were laboratory confirmed; therefore, it is possible that some individuals
presenting with ILI were not due to A(H1N1) pdm09 infection. However, it is unlikely that this would have a major impact on the results given the high positivity rate of those laboratory samples that were tested, and the fact that no other respiratory viruses were identified. We consider it more probable the true attack rate was in fact higher than we demonstrate, as case ascertainment relied on patients self-presenting to medical care and, of those, some 21 listed in the clinic log as presenting with ILI did not have locatable medical records and so could not be included in our study. Risk factors associated with disease need to be interpreted with caution as there was no comparison group, and medical records may lack accuracy. For example, smoking would be expected to be a risk factor for influenza;38 however, only 10% of adult cases were recorded as being smokers compared with a self-reported smoking prevalence across the region of 29.5%.28 In addition, if patients were vaccinated in another location this would not have been captured by the clinic medical records, which would result in an underestimation of the vaccination coverage rate in the community. While we reviewed the WANIDD system and patients’ notes for previous cases of A(H1N1) pdm09, it is possible that cases had occurred in 2009 or subsequent years that were not captured in either of these sources. Ideally, notes of all individuals in the community (rather than cases only) would have been reviewed for prior evidence of A(H1N1) pdm09 infection; however, due to limited resources in the acute outbreak setting this was not possible. Evaluation of the uptake of social distancing and hand washing alerts by community members was not undertaken following this outbreak. Appropriate evaluation of the success of these measures should be considered by investigators in similar future outbreaks.
Implications This study confirms that influenza outbreaks in Aboriginal communities should be considered a high public health priority.17,27,39 There are learning opportunities in regards to early diagnosis, prioritisation of control measures and management for at-risk groups during an influenza outbreak.27,39
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Local implications have been aimed at increasing the rapidity of outbreak reporting. Due to late notification, the response to this event was not very timely and most likely had limited impact on preventing further cases. Part of the delay was unavoidable as it was caused by the community’s isolation and consequent difficulty in obtaining laboratory confirmation of the cause of the outbreak. However, recognition and reporting of the outbreak by clinical staff was also delayed. As a result, clearer reporting procedures for suspected outbreaks have been developed for the region and improved communication established with acute care services. More broadly, despite the clear importance of preventive measures for remote communities, it remains difficult for remote area clinic nurses and health workers to prioritise activities such as community vaccination when the health service is constantly overwhelmed by acute health care demands. To prevent influenza outbreaks, it is important for the public health sector to continue to advocate for adequate human resources to ensure community vaccination programs for influenza are implemented effectively. Additionally, vaccination campaigns in preparation for ‘influenza season’ in tropical regions should be undertaken early. The seasonality of influenza virus is clearly described in temperate regions14,40 and it is recommended that vaccination be undertaken in autumn, in anticipation of winter outbreaks of influenza.10 In Western Australia, the annual influenza vaccine is made available from around mid-March for this reason. However, less has been known about the seasonality of influenza in the tropics and preparing for ‘influenza season’ in tropical northern Australia is challenging, as the most appropriate timing for vaccination campaigns has previously been unclear.6 This outbreak confirms the Australian Immunisation Handbook recommendation that vaccination be given as early as February in tropical areas,10 and provides a sound argument for the earlier availability of the annual influenza vaccine in tropical Australia in order to undertake early vaccination campaigns. In this outbreak, a large number of cases had received A(H1N1)pdm09-containing vaccine since 2009, yet became ill in 2013. Thus, the public health message of annual influenza vaccine should continue. In addition, as immunity to the annual influenza vaccination is known to wane, annual
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education campaigns on the importance of hand washing, social distancing when ill and other associated hygiene practices should be undertaken by public health units in conjunction with community organisations and leaders. Finally, this influenza outbreak has implications for pandemic planning. Previously, there was no Australian literature available describing the effect of an outbreak of a novel influenza strain on a single remote Aboriginal community and the associated public health response. This outbreak provides evidence that remote communities that may be isolated from initial waves of pandemics should have ongoing preventative measures for many years to reduce susceptibility to novel strains. This report confirms that young Aboriginal children should be considered at risk of hospitalisation and targeted during vaccination campaigns to reduce susceptibility to the complications of influenza.
Conclusion This is the first published description of what was essentially a novel influenza strain on a single remote Australian Aboriginal community. Isolation and low vaccination coverage explain the apparent naivety to the A(H1N1)pdm09 virus, and raise the possibility that there may be other remote Aboriginal communities in Australia remaining at risk. High attack and complication rates confirm that Aboriginal people should be a priority in pandemic planning.6,27,39 Policy changes via consideration of early vaccination, increased public health support for community immunisation campaigns and prioritisation measures during outbreaks are required to ensure that remote Aboriginal communities are prioritised in pandemics and before each influenza season.
Acknowledgements The authors acknowledge the Aboriginal community and its people where the outbreak took place. The authors wish to thank the following individuals for their assistance or advice: Ms Hilary Carmichael, Ms Katy Crawford, Ms Ashley Eastwood, Ms Monica Frain, Ms Bec Morgan-Dann, Professor Heath Kelly, Professor Geoff Mercer (deceased), Ms Carolien Giele and Professor David Atkinson.
Philippa Chidgzey receives a scholarship funded by the Western Australian Department of Health.
References 1. Flint S, Davis J, Su J-Y, Oliver-Landry E, Rogers B, Goldstein A, et al. Disproportionate impact of pandemic (H1N1) 2009 influenza on Indigenous people in the Top End of Australia’s Northern Territory. Med J Aust. 2010;192(10):617-22. 2. Kelly H. A pandemic response to a disease of predominantly seasonal intensity. Med J Aust. 2010;192(2):81-3. 3. Rudge S, Massey P. Responding to Pandemic 2009 Influenza (H1N1) in Aboriginal Communities in NSW through collaboration with NSW Health and the Aboriginal Community Controlled health sector. NSW Public Health Bull. 2010;21:1-2. 4. Kelly H, Mercer G, Cheng A. Quantifying the risk of pandemic influenza in pregnancy and indigenous people in Australia in 2009. Euro Surveill. 2009;14(50): pii: 19441. PubMed PMID: 20070939 5. La Ruche G, Tarantola A, Barboza P, Vaillant L, Gueguen J, Gastellu-Etchegorry M. The 2009 pandemic H1N1 influenza and indigenous populations of the Americas and the Pacific. Euro Surveill. 2009;14(42). pii: 19366. PubMed PMID: 19883543 6. Couzos S, Murray R. Aboriginal Primary Health Care: An Evidence-based Approach. 3rd ed. South Melbourne (AUST): Oxford University Press; 2008. 7. Scalera N, Mossad S. The first pandemic of the 21st century: A review of the 2009 pandemic variant influenza A (H1N1) virus. Postgrad Med. 2009;121(5):43. 8. Reed C, Meltzer MI, Finelli L, Fiore A. Public health impact of including two lineages of influenza B in a quadrivalent seasonal influenza vaccine. Vaccine. 2012;30(11):1993-8. 9. Valkenburg SA, Rutigliano JA, Ellebedy AH, Doherty PC, Thomas PG, Kedzierska K. Immunity to seasonal and pandemic influenza A viruses. Microbes Infect. 2011;13(5):489-501. 10. Department of Health and Ageing. Australian Immunisation Handbook. 10th ed: Canberra (Aust): Commonwealth of Australia; 2013. 11. Mostaco-Guidolin LC, Towers SM, Buckeridge DL, Moghadas SM. Age distribution of infection and hospitalization among Canadian First Nations populations during the 2009 H1N1 pandemic. Am J Public Health. 2013;103(2):e39-44. 12. Mostaco-Guidolin L, Greer A, Sander B, Wu J, Moghadas S. Variability in transmissibility of the 2009 H1N1 pandemic in Canadian communities. BMC Res Notes. 2011;4(1):537. 13. Chowell G, Miller M, Viboud C. Seasonal influenza in the United States, France, and Australia: transmission and prospects for control. Epidemiol Infect. 2008;136(6): 852-64. 14. Tamerius J, Nelson MI, Zhou SZ, Viboud C, Miller MA, Alonso WJ. Global influenza seasonality: Reconciling patterns across temperate and tropical regions. Environ Health Perspect. 2011;119(4):439-45. 15. Pollock SL, Sagan M, Oakley L, Fontaine J, Poffenroth L. Investigation of a pandemic H1N1 influenza outbreak in a remote First Nations community in northern Manitoba, 2009. Can J Public Health. 2012;103(2):90-3. 16. Baker MG, Wilson N, Huang QS, Paine S, Lopez L, Bandaranayake D, et al. Pandemic influenza A(H1N1)v in New Zealand: The experience from April to August 2009. Euro Surveill. 2009;14(34). pii: 19319. PubMed PMID: 19712648 17. Communicable Diseases Network Australia. Influenza Infection: CDNA National Guidelines For Public Health Units. Canberra (AUST): Commonwealth Department of Health; 2011. 18. Australian Bureau of Statistics. 2011 Census of Population and Housing: Basic Community Profile. Canberra (AUST): ABS; 2011. 19. Australian Institute of Health and Welfare. The Health and Welfare of Australia’s Aboriginal and Torres Strait Islander People, An Overview 2011. Canberra (AUST): AIHW; 2011.
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20. Australian Indigenous HealthInfoNet. Review of the Impact of Housing and Health-related Infrastructure on Indigenous Health [Internet]. Perth (AUST): Edith Cowan University Australian Indigenous Health InfoNet; 2008 [cited 2013 Oct 15]. Available from: http://www. healthinfonet.ecu.edu.au/determinants/physicalenvironment/reviews/our-review 21. PathWest Laboratory Medicine Western Australia. Online Test Directory. Perth (AUST): State Government of Western Australia; 2012. 22. Van Kerkhove MD, Vandemaele KA, Shinde V, JaramilloGutierrez G, Koukounari A, Donnelly CA, et al. Risk factors for severe outcomes following 2009 influenza A (H1N1) infection: a global pooled analysis. PLoS Med. 2011;8(7):e1001053. 23. Rothberg M, Haessler S, Brown R. Complications of Viral Influenza. Am J Med. 2008;121(4):258-64. 24. Health Protection Surveillance Centre. Enhanced Surveillance Form for Confirmed Hospitalised Influenza Cases Aged 0-14 Years. 1.9 ed. Dublin (IRL): Health Service Executive; 2012. 25. Centers for Disease Control and Prevention. Epi Info 7 [Internet]. Atlanta (GA): CDC; 2008 [cited 2013 Mar 18]. Available from: http://wwwn.cdc.gov/epiinfo/ 26. Communicable Disease Control Directorate. Notifiable Infectious Diseases Database. Notifiable Infectious Disease Reports. Perth (AUST): Western Australia Department of Health; 2013. 27. Massey PD, Miller A, Saggers S, Durrheim DN, Speare R, Taylor K, et al. Australian Aboriginal and Torres Strait Islander communities and the development of pandemic influenza containment strategies: Community voices and community control. Health Policy. 2011;103(2–3):184-90.
20
28. Western Australia Country Health Service. Kimberley Health Profile. Perth (AUST): State Government of Western Australia; 2012. 29. Van Kerkhove M, Hirve S, Koukounari A, Mounts A. Estimating Age-Specific Cumulative Incidence for the 2009 Influenza Pandemic: A Meta-Analysis of A(H1N1) pdm09 Serological Studies from 19 countries. Influenza Other Respir Viruses. 2013;7(5):872–86. 30. Janjua NZ, Skowronski DM, Hottes TS, Osei W, Adams E, Petric M, et al. Transmission dynamics and risk factors for pandemic H1N1-related illness: Outbreak investigation in a rural community of British Columbia, Canada. Influenza Other Respir Viruses. 2012;6(3):e54-e62. PubMed PMID: 22385647 31. Chang Y-S, vanHal SJ, Spencer PM, Gosbell IB, Collett PW. Comparison of adult patients hospitalised with pandemic (H1N1) 2009 influenza and seasonal influenza during the“PROTECT”phase of the pandemic response. Med J Aust. 2010;192(2):90-3. 32. Denholm JT, Gordon CL, Johnson PD, Hewagam SS, Stuart RL, Aboltins C, et al. Hospitalised adult patients with pandemic (H1N1) 2009 influenza in Melbourne, Australia. Med J Aust. 2010;192(2):84-6. 33. Haysom L, Williams R, Hodson EM, Lopez-Vargas PA, Roy LP, Lyle DM, et al. Natural history of chronic kidney disease in Australian Indigenous and non-Indigenous children: A 4-year population-based follow-up study. Med J Aust. 2009;190(6):303-6. 34. Menzies R, Turnour C, Chiu C, McIntyre P. Vaccine preventable diseases and vaccination coverage in Aboriginal and Torres Strait Islander people, Australia 2003 to 2006. Commun Dis Intell Q Rep. 2008;32 Suppl:S2-67.
35. Naidu L, Chiu C, Habig A, Lowbridge C, Jayasinghe S, Wang H, et al. Vaccine preventable diseases and vaccination coverage in Aboriginal and Torres Strait Islander people, Australia 2006-2010. Commun Dis Intell Q Rep. 2013;37 Suppl:S1-95. 36. Quinones-Parra S, Grant E, Loh L, Nguyen TH, Campbell KA, Tong SY, et al. Preexisting CD8+ T-cell immunity to the H7N9 influenza A virus varies across ethnicities. Proc Natl Acad Sci U S A. 2014;111(3):1049-54. 37. Dockery AM, Colquhoun S. Mobility of Aboriginal and Torres Strait Islander People: A Literature Review. Cooperative Research Centre for Remote Economic Participation (CRC-REP) Working Paper CW004. Alice Springs (AUST): Ninti One Limited; 2012. 38. Arcavi L, Benowitz NL. Cigarette smoking and infection. Arch Intern Med. 2004;164(20):2206-16. 39. Miller A, Durrheim AD. Aboriginal and Torres Strait Islander communities forgotten in new Australian National Action Plan for Human Influenza Pandemic: “Ask us, listen to us, share with us”. Med J Aust. 2010;193(6):316-7. 40. Lowen AC, Mubareka S, Steel J, Palese P. Influenza virus transmission is dependent on relative humidity and temperature. PLoS Pathog. 2007;3(10):1470-6.
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An outbreak of influenza A (H1N1) virus in a remote Aboriginal community post-pandemic: implications for pandemic planning and health service policy Philippa J. Chidgzey,1,2 Stephanie Davis,2 Peta Williams,1 Carole Reeve1
A
boriginal people were disproportionately affected in the influenza pandemic of 2009.1 The pandemic had a less severe impact on the general population than originally anticipated;2 however, Aboriginal people were more likely to require admission to hospital and more likely to die from influenza than non-Aboriginal Australians.1,3,4 In addition, the 2009 pandemic confirmed that Aboriginal people experience the complications of the influenza virus, whether pandemic or seasonal strains, more often than the non-Aboriginal Australian population.1,4,5 Reasons for these disparities are multifactorial, including high prevalence of chronic diseases, high pregnancy rates and socioeconomic factors such as reduced access to health care and barriers to health-seeking behaviour.1,5,6 Since causing the pandemic in 2009, the influenza A(H1N1) virus (abbreviated as A(H1N1)pdm09)2,7 has been circulating in the Australian population and is now considered a seasonal strain. The strain has been incorporated into the trivalent seasonal influenza vaccine since 2010.8 The general population is no longer considered to be A(H1N1)pdm09 naïve due to previous exposure or vaccination.9 Thus, the strain is not expected to cause greater morbidity or mortality than other seasonal strains. As currently available seasonal influenza vaccines confer protection for about a year, annual vaccination is required for ongoing protection.10
Abstract Objective: To describe a 2013 outbreak of pandemic influenza A (H1N1) virus in a remote Western Australian Aboriginal community; inform outbreak prevention and control measures and discuss the community susceptibility to H1N1, three years after the A(H1N1)pdm09 pandemic. Methods: Records at the local clinic were used to classify cases as ‘confirmed’ (laboratory test positive for H1N1 or temperature >38°C with cough and/or sore throat) or ‘probable’ (selfreported fever with cough and/or sore throat). Additional data were collected from medical records and public health databases. Results: A total of 108 individuals met case definitions. Clinical attack rate was 23%. Children under five years of age had the highest age-specific attack rate (545 per 1,000 population). Thirty cases (28%) experienced complications with six (5.6%) requiring aero-evacuation. Only 7% of the community had received H1N1-containing vaccine during the previous year. No H1N1 cases from the community were previously reported. Conclusions: This is the first description of the effects of a novel influenza strain on a remote Australian Aboriginal community. Isolation and low vaccination are likely explanations for the apparent naivety to H1N1. Implications: There may be other remote communities at risk of H1N1. High attack and complication rates confirm that Aboriginal Australians should be prioritised in pandemic planning. Key words: outbreak, influenza, Aboriginal, remote, susceptibility Globally, Aboriginal populations are at higher risk of increased exposure, clinical infection, complications and consequences of influenza. Socioeconomic and cultural circumstances often determine that large families live together.11,12 Overcrowding leads to increased transmission of the influenza virus,13,14 resulting in high influenza attack rates in Indigenous populations internationally.11,15,16 Aboriginal people in Australia also are known to be an at-risk group for influenza;2,17 however, less is known about the natural
history of the influenza virus within remote Aboriginal communities. In March 2013, a paediatrician reported a suspected outbreak of influenza-like illness (ILI) in a remote Aboriginal community in north-west Western Australia to the regional population health unit. An investigation was conducted by the regional population health unit with the following objectives: to describe and control the outbreak; to determine why the community had remained vulnerable to A(H1N1)pdm09 more than three years after
1. Kimberley Population Health Unit, Western Australia Country Health Service, WA 2. National Centre for Epidemiology and Population Health, ANU College of Medicine and Health Sciences, Australian National University, ACT Correspondence to: Dr Philippa J. Chidgzey, Kimberley Population Health Unit, Western Australia Country Health Service, PO Box 525, Broome, WA 6725; e-mail: [email protected] Submitted: May 2014; Revision requested: June 2014; Accepted: August 2014 The authors have stated they have no conflict of interest. Aust NZ J Public Health. 2015; 39:15-20; doi: 10.1111/1753-6405.12295
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the 2009 pandemic; and to inform prevention and control measures for future influenza outbreaks in remote Aboriginal communities.
Methods
cardiovascular complications, neurological complications, encephalitis, Reye syndrome, renal dysfunction, liver dysfunction, bone marrow dysfunction or other documented complication.10,23,24
Outbreak setting
Epidemiological investigation
The remote community has no road access for most of the year due to tropical rains and is accessed by aeroplane or boat. The population size fluctuates and is estimated at 400 to 500 residents.18 There is a relatively young age distribution, as is common in Aboriginal communities.6,19 Housing is limited and overcrowding is common.20 The community is serviced by a nurse-led remote area clinic with a visiting doctor service two days per week.
The clinic log, which codes every patient presentation according to clinical signs and symptoms, was reviewed for the dates from 25 February 2013 to 8 April 2013. Electronic and paper records were then reviewed for all patients with presentations coded as ILI to determine whether they met the outbreak case definition and, if so, to collect further details about each case including demographic details, risk factors for complications, vaccination status, symptoms, complications, treatment and tests performed. Individuals were excluded from all counts, figures and analysis if the medical record could not be located. Data were entered and analysed using Epi Info 7.25
Case definitions Outbreak case definitions were modified from the Communicable Diseases Network Australia (CDNA) influenza guidelines for public health units.17 A confirmed case was defined as a community resident and either laboratory confirmed with laboratory test positive for H1N1 or clinically confirmed with measured temperature of >38°C at time of clinic presentation with cough and/or sore throat, with onset from 25 February 2013 to 8 April 2013. A probable case was defined as a community resident with self-reported fever with cough and/or sore throat with onset between 25 February 2013 to 8 April 2013.17 Laboratory testing was undertaken via dry throat swab polymerase chain reaction (PCR) assay of influenza A virus H1N109 RNA.21 Dry swabs were transported by aeroplane to the public health reference laboratory in Western Australia for testing. Other viruses tested for in the respiratory panel were Adenovirus, Enterovirus/ Rhinovirus, Human Metapneumovirus, Influenza B virus, Parainfluenza 1,2 and 3 and Respiratory Syncytial Virus.21 Both probable and confirmed ILI cases were included in the numerator. Risk factors for severe influenza were taken from the CDNA influenza guidelines for public health units.17 Severe influenza was considered to be the requirement for hospitalisation, admission to intensive care units or death.22,23 A complication was recorded if there was clinical documentation of any of the following features: primary or secondary bacterial pneumonia, bronchitis, croup, acute otitis media,
16
Overall and age specific attack rates were calculated using 2011 census data.18 To examine community susceptibility to H1N1, the Western Australian Notifiable Infectious Diseases Database (WANIDD)26 was reviewed for prior cases of A(H1N1)pdm09 in the community. Case clinic notes were also reviewed for previous presentations of ILI. Community immunisation coverage from 2009 to 2013 was determined via review of the public health immunisation database that collects immunisation data from both adults and children in the Kimberley (HCare) and the clinic electronic medical record system.
Results The outbreak was first reported by clinical staff on 12 March 2013 as a cluster of eight children presenting with ILI and haematuria on urine dipstick. Initial reports considered an arbovirus as a possible cause; however, six specimens tested positive for influenza A(H1N1)pdm09 virus on Saturday 16 March 2013. The outbreak investigation and response followed. According to the clinic log, 129 patients presented with ILI during the outbreak time period. Of these, medical records could be located for 108 patients, all of whom met the outbreak case definitions. This gave a clinical attack rate of 23%. Seventy individuals (65%) met the definition for a confirmed case while 38 (35%) met the definition for a probable case. Thirty cases (27%) had swab samples sent for testing. Influenza A(H1N1)pdm09 virus was detected in 27 of these (90%). Figure 1 shows the epidemic curve. The case with the earliest date of illness onset did not report any travel outside of the community during the previous two weeks (27/2/2013); however, the case with the second earliest date of illness onset (28/3/2013) had travelled throughout the Kimberley region by bus five days prior to symptom onset.
Characteristics of cases The median age of cases was 11.5 years ranging from zero to 80 years. The majority of cases were children with 23 cases aged
Figure 1: Epidemic curve of the remote community outbreak by outbreak case definition.
* Confirmed cases include both laboratory confirmed and clinically confirmed cases.
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five to nine years (20%). Figure 2 shows the age-specific attack rates. Those aged zero to four years had the highest age-specific rates. Males made up 33% of cases (n=36) and 67% of cases were female (n=72). When examined by risk factors for severe influenza,17,22 10 cases (9%) were under two years of age and 104 (95%) were Aboriginal people. Eleven cases (10%) had a record of smoking, 17 (16%) had documented chronic lung disease (chronic obstructive pulmonary disease or asthma), nine (8%) had congenital or chronic heart disease, 10 (9%) had chronic renal disease, 15 (14%) had type 2 diabetes mellitus and one case had a known pregnancy. Table 1 shows the proportions of cases with symptoms, signs and complications as documented in medical records. Proportions of laboratory confirmed cases with risk factors for severe influenza were similar to the overall case group (results not shown). Six cases (5.6%) were flown out of community for hospitalisation. Reasons for these aeromedical evacuations were secondary bacterial pneumonia, febrile convulsion, dehydration and croup. No cases of encephalitis, Reyes syndrome, cardiovascular complications or multi-organ complications were reported. There were no documented fatalities.
On initiation of the investigation, alerts were sent by the population health unit to the community clinic, regional hospital doctors
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Three findings deserve particular mention. First, the clinical attack rate of 23% was higher
* Confirmed cases include both laboratory confirmed and clinically confirmed cases.
Table 1: Number and proportions of symptoms, signs and outcomes recorded in medical notes. Factor
Control measures
To our knowledge, this is the first described outbreak of influenza A(H1N1)pdm09 virus in a remote Australian Aboriginal community to be systematically investigated. The outbreak had a large impact on a community already burdened by a high prevalence of underlying medical conditions.28 The high attack and complication rates suggest that the community was most likely H1N1 naïve due to low vaccination coverage and lack of previous exposure to the A(H1N1)pdm09 virus as a result of isolation.
Figure 2: Age specific attack rates per 1000 population by outbreak case definition.
Number and proportion of cases with symptom/ sign or outcome
Immunity or previous exposure Prior to the outbreak, there had never been a case of A(H1N1)pdm09 from the community recorded on WANIDD. In addition, one current outbreak case had presented during the influenza pandemic of 2009 and was laboratory test negative for A(H1N1)pdm09 virus and other influenza strains at that time. As at 20 March 2013, the annual community influenza vaccination coverage rate was estimated at 7%. Of the identified cases in this outbreak, 11 were documented as having been vaccinated in 2012 with the seasonal trivalent influenza vaccine. Additionally, 32 cases (30%) received single valent A(H1N1) pdm09-containing Panvax® in 2009/2010. Overall, 46 cases (43%) had ever received either a single valent or trivalent A(H1N1) pdm09-containing influenza vaccine since 2009.
Discussion
and Aboriginal Medical Services advising of the current outbreak, influenza treatment guidelines,17 vaccination recommendations10 and information for patients regarding control measures including social distancing and hand washing.17,27 Lay language alerts were displayed outside the community clinic, shop and school. Copies were also provided to the community council for distribution to community residents. Over the following days, supplies of vaccinations and Oseltamivir for specific cases17 were dispatched to the community. Two cases received treatment with Oseltamivir. Clinic nurses and a team from regional disease control provided 160 influenza vaccinations within 2.5 days.
Total number of cases
Number and proportion of laboratory confirmed cases with symptom/ sign or outcome
Number and proportion of cases aged less than 5 years
Number and proportion of cases aged 5-12 years
Number and proportion of cases aged greater than 12 years
108
27 (25%)
24 (22%)
32 (30%)
52 (48%)
Temperature >38° C
63 (59%)
20 (74%)
16 (25%)
25 (40%)
22 (35%)
Cough
88 (82%)
20 (74%)
21 (24%)
25 (28%)
42 (48%)
Sore Throat
48 (44%)
13 (48%)
5 (10%)
13 (27%)
30 (63%)
Headachea
28 (26%)
8 (30%)
1(4%)
8 (29%)
19 (68%)
Gastrointestinal upset
17 (16%)
8 (30%)
7 (41%)
3 (18%)
7 (41%)
8 (7%)
5 (19%)
1 (13%)
4 (50%)
3 (38%)
Symptoms/Signs
Haematuria on urine dipstick
a
Outcomes Hospitaliseda
6 (6%)
5 (19%)
4 (67%)
1 (17%)
1 (17%)
Complication
31 (29%)
11 (41%)
11 (36%)
10 (32%)
10 (32%)
8 (7%)
4 (15%)
2 (25%)
0
6 (75%)
Secondary Bacterial Pneumonia Bronchitis
7 (7%)
0
0
4 (57%)
3 (43%)
Acute Otitis Media
5 (5%)
3 (11%)
3 (60%)
1 (20%)
1 (20%)
Croup
2 (2%)
0
2 (100%)
0
0
Neurological complicationsb
2 (2%)
2(7%)
1 (50%)
1 (50%)
0
Complication-other
7 (6%)
2 (7%)
3 (43%)
4 (57%)
0
a: Age-specific proportions do not equate to 100% due to rounding b: seizure or hallucinations
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than findings from other pandemic H1N1 publications in the general population.7,29 Secondly, female cases predominated in the adult age group, potentially a reflection of differences in health seeking behaviour between genders, and/or differences in child-care responsibilities. Thirdly, as reported elsewhere, there were high age-specific attack rates in the younger age groups.7,11,29,30 While the epidemiology of A(H1N1) pdm09 has been well described in many populations,22,30-32 data regarding the effect of H1N1 on remote Australian Aboriginal populations have remained scarce.1 To our knowledge there are no other published reports of a pandemic influenza outbreak in a remote Australian community for comparison. However, our findings are similar to a report from a remote Indigenous community in Canada that showed a similar attack rate with little difference in characteristics between laboratory confirmed and probable cases. Young children were disproportionately affected, as was the case in this outbreak.15 A feature of this outbreak that has not been described in other A(H1N1)pdm09 reports1,31,32 was the presence of microscopic haematuria on urine dipstick in eight children. Haematuria has not previously been recognised as a complication of seasonal influenza either.23 However, the significance of this finding in the setting of febrile illness is unclear. First, the haematuria was found only on urine dipstick and not laboratory confirmed. Second, not all cases were tested for haematuria and the prevalence of haematuria in the community is not available. While there have been limited studies on the prevalence of haematuria in Aboriginal children living in remote Australia,33 anecdotally, incidental haematuria is a not infrequent finding in both well and febrile children. The community was likely to have been susceptible to this outbreak for several reasons, one of these being because the annual vaccination coverage was low. The CDNA recommended the target of 50% coverage to contain community transmission of H1N1 in the pandemic year.17 The calculated 7% coverage rate estimated for this community fell well short of this target. Recently published data for comparison of adult coverage rates in other remote communities is scarce. However, a Communicable Disease Intelligence publication reported vaccination coverage in
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other remote Western Australian Aboriginal populations in 2005, with 65% of remote Aboriginal people aged 50-64 years and 20% of Aboriginal people aged 15-49 years receiving influenza vaccine within the previous 12 months.34 A 2013 updated report did not include influenza vaccination coverage35 for a more recent comparison. Another contributing factor to the community’s vulnerability to an outbreak was the apparent naivety to A(H1N1)pdm09 virus. The primary circulating influenza strain across the Kimberley region in 2009 was pandemic H1N1.26 Thus, it was originally assumed that most of the regional population would have been exposed to the circulating virus at some point. By contrast, there had never been a notification captured by WANIDD of A(H1N1)pdm09 virus originating from this particular community prior to this outbreak.26 Further, senior community members reported to the investigation team that no “swine flu” occurred in the community during the pandemic influenza year. Additionally, ongoing research in influenza A(H7N9) has suggested that Aboriginal populations may lack genetic cross-protective immunity against pandemic influenza strains.36 According to WANIDD,26 there were isolated A(H1N1)pdm09 cases in two other communities in March 2013 with no further transmission recorded in either area. In addition, A(H1N1)pdm09 virus was introduced into another remote community (community B) at the same time the outbreak was progressing. Transmission ceased in community B at six cases. Community B had both notified cases of previous A(H1N1) pdm09 virus and high community vaccination levels against influenza, supporting our conclusion that the H1N1 naivety of the community where the outbreak occurred was central to the epidemic.
Study limitations There are a number of limitations to this study. In this setting, defining an accurate denominator population is always challenging given the high mobility of remote Aboriginal people.37 However, we consider the Australian Bureau of Statistics (ABS) population estimate to be reasonably accurate as this was very similar to the population figure held by the clinic (unpublished data). Not all cases were laboratory confirmed; therefore, it is possible that some individuals
presenting with ILI were not due to A(H1N1) pdm09 infection. However, it is unlikely that this would have a major impact on the results given the high positivity rate of those laboratory samples that were tested, and the fact that no other respiratory viruses were identified. We consider it more probable the true attack rate was in fact higher than we demonstrate, as case ascertainment relied on patients self-presenting to medical care and, of those, some 21 listed in the clinic log as presenting with ILI did not have locatable medical records and so could not be included in our study. Risk factors associated with disease need to be interpreted with caution as there was no comparison group, and medical records may lack accuracy. For example, smoking would be expected to be a risk factor for influenza;38 however, only 10% of adult cases were recorded as being smokers compared with a self-reported smoking prevalence across the region of 29.5%.28 In addition, if patients were vaccinated in another location this would not have been captured by the clinic medical records, which would result in an underestimation of the vaccination coverage rate in the community. While we reviewed the WANIDD system and patients’ notes for previous cases of A(H1N1) pdm09, it is possible that cases had occurred in 2009 or subsequent years that were not captured in either of these sources. Ideally, notes of all individuals in the community (rather than cases only) would have been reviewed for prior evidence of A(H1N1) pdm09 infection; however, due to limited resources in the acute outbreak setting this was not possible. Evaluation of the uptake of social distancing and hand washing alerts by community members was not undertaken following this outbreak. Appropriate evaluation of the success of these measures should be considered by investigators in similar future outbreaks.
Implications This study confirms that influenza outbreaks in Aboriginal communities should be considered a high public health priority.17,27,39 There are learning opportunities in regards to early diagnosis, prioritisation of control measures and management for at-risk groups during an influenza outbreak.27,39
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Local implications have been aimed at increasing the rapidity of outbreak reporting. Due to late notification, the response to this event was not very timely and most likely had limited impact on preventing further cases. Part of the delay was unavoidable as it was caused by the community’s isolation and consequent difficulty in obtaining laboratory confirmation of the cause of the outbreak. However, recognition and reporting of the outbreak by clinical staff was also delayed. As a result, clearer reporting procedures for suspected outbreaks have been developed for the region and improved communication established with acute care services. More broadly, despite the clear importance of preventive measures for remote communities, it remains difficult for remote area clinic nurses and health workers to prioritise activities such as community vaccination when the health service is constantly overwhelmed by acute health care demands. To prevent influenza outbreaks, it is important for the public health sector to continue to advocate for adequate human resources to ensure community vaccination programs for influenza are implemented effectively. Additionally, vaccination campaigns in preparation for ‘influenza season’ in tropical regions should be undertaken early. The seasonality of influenza virus is clearly described in temperate regions14,40 and it is recommended that vaccination be undertaken in autumn, in anticipation of winter outbreaks of influenza.10 In Western Australia, the annual influenza vaccine is made available from around mid-March for this reason. However, less has been known about the seasonality of influenza in the tropics and preparing for ‘influenza season’ in tropical northern Australia is challenging, as the most appropriate timing for vaccination campaigns has previously been unclear.6 This outbreak confirms the Australian Immunisation Handbook recommendation that vaccination be given as early as February in tropical areas,10 and provides a sound argument for the earlier availability of the annual influenza vaccine in tropical Australia in order to undertake early vaccination campaigns. In this outbreak, a large number of cases had received A(H1N1)pdm09-containing vaccine since 2009, yet became ill in 2013. Thus, the public health message of annual influenza vaccine should continue. In addition, as immunity to the annual influenza vaccination is known to wane, annual
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education campaigns on the importance of hand washing, social distancing when ill and other associated hygiene practices should be undertaken by public health units in conjunction with community organisations and leaders. Finally, this influenza outbreak has implications for pandemic planning. Previously, there was no Australian literature available describing the effect of an outbreak of a novel influenza strain on a single remote Aboriginal community and the associated public health response. This outbreak provides evidence that remote communities that may be isolated from initial waves of pandemics should have ongoing preventative measures for many years to reduce susceptibility to novel strains. This report confirms that young Aboriginal children should be considered at risk of hospitalisation and targeted during vaccination campaigns to reduce susceptibility to the complications of influenza.
Conclusion This is the first published description of what was essentially a novel influenza strain on a single remote Australian Aboriginal community. Isolation and low vaccination coverage explain the apparent naivety to the A(H1N1)pdm09 virus, and raise the possibility that there may be other remote Aboriginal communities in Australia remaining at risk. High attack and complication rates confirm that Aboriginal people should be a priority in pandemic planning.6,27,39 Policy changes via consideration of early vaccination, increased public health support for community immunisation campaigns and prioritisation measures during outbreaks are required to ensure that remote Aboriginal communities are prioritised in pandemics and before each influenza season.
Acknowledgements The authors acknowledge the Aboriginal community and its people where the outbreak took place. The authors wish to thank the following individuals for their assistance or advice: Ms Hilary Carmichael, Ms Katy Crawford, Ms Ashley Eastwood, Ms Monica Frain, Ms Bec Morgan-Dann, Professor Heath Kelly, Professor Geoff Mercer (deceased), Ms Carolien Giele and Professor David Atkinson.
Philippa Chidgzey receives a scholarship funded by the Western Australian Department of Health.
References 1. Flint S, Davis J, Su J-Y, Oliver-Landry E, Rogers B, Goldstein A, et al. Disproportionate impact of pandemic (H1N1) 2009 influenza on Indigenous people in the Top End of Australia’s Northern Territory. Med J Aust. 2010;192(10):617-22. 2. Kelly H. A pandemic response to a disease of predominantly seasonal intensity. Med J Aust. 2010;192(2):81-3. 3. Rudge S, Massey P. Responding to Pandemic 2009 Influenza (H1N1) in Aboriginal Communities in NSW through collaboration with NSW Health and the Aboriginal Community Controlled health sector. NSW Public Health Bull. 2010;21:1-2. 4. Kelly H, Mercer G, Cheng A. Quantifying the risk of pandemic influenza in pregnancy and indigenous people in Australia in 2009. Euro Surveill. 2009;14(50): pii: 19441. PubMed PMID: 20070939 5. La Ruche G, Tarantola A, Barboza P, Vaillant L, Gueguen J, Gastellu-Etchegorry M. The 2009 pandemic H1N1 influenza and indigenous populations of the Americas and the Pacific. Euro Surveill. 2009;14(42). pii: 19366. PubMed PMID: 19883543 6. Couzos S, Murray R. Aboriginal Primary Health Care: An Evidence-based Approach. 3rd ed. South Melbourne (AUST): Oxford University Press; 2008. 7. Scalera N, Mossad S. The first pandemic of the 21st century: A review of the 2009 pandemic variant influenza A (H1N1) virus. Postgrad Med. 2009;121(5):43. 8. Reed C, Meltzer MI, Finelli L, Fiore A. Public health impact of including two lineages of influenza B in a quadrivalent seasonal influenza vaccine. Vaccine. 2012;30(11):1993-8. 9. Valkenburg SA, Rutigliano JA, Ellebedy AH, Doherty PC, Thomas PG, Kedzierska K. Immunity to seasonal and pandemic influenza A viruses. Microbes Infect. 2011;13(5):489-501. 10. Department of Health and Ageing. Australian Immunisation Handbook. 10th ed: Canberra (Aust): Commonwealth of Australia; 2013. 11. Mostaco-Guidolin LC, Towers SM, Buckeridge DL, Moghadas SM. Age distribution of infection and hospitalization among Canadian First Nations populations during the 2009 H1N1 pandemic. Am J Public Health. 2013;103(2):e39-44. 12. Mostaco-Guidolin L, Greer A, Sander B, Wu J, Moghadas S. Variability in transmissibility of the 2009 H1N1 pandemic in Canadian communities. BMC Res Notes. 2011;4(1):537. 13. Chowell G, Miller M, Viboud C. Seasonal influenza in the United States, France, and Australia: transmission and prospects for control. Epidemiol Infect. 2008;136(6): 852-64. 14. Tamerius J, Nelson MI, Zhou SZ, Viboud C, Miller MA, Alonso WJ. Global influenza seasonality: Reconciling patterns across temperate and tropical regions. Environ Health Perspect. 2011;119(4):439-45. 15. Pollock SL, Sagan M, Oakley L, Fontaine J, Poffenroth L. Investigation of a pandemic H1N1 influenza outbreak in a remote First Nations community in northern Manitoba, 2009. Can J Public Health. 2012;103(2):90-3. 16. Baker MG, Wilson N, Huang QS, Paine S, Lopez L, Bandaranayake D, et al. Pandemic influenza A(H1N1)v in New Zealand: The experience from April to August 2009. Euro Surveill. 2009;14(34). pii: 19319. PubMed PMID: 19712648 17. Communicable Diseases Network Australia. Influenza Infection: CDNA National Guidelines For Public Health Units. Canberra (AUST): Commonwealth Department of Health; 2011. 18. Australian Bureau of Statistics. 2011 Census of Population and Housing: Basic Community Profile. Canberra (AUST): ABS; 2011. 19. Australian Institute of Health and Welfare. The Health and Welfare of Australia’s Aboriginal and Torres Strait Islander People, An Overview 2011. Canberra (AUST): AIHW; 2011.
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19
Chidgzey et al.
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20. Australian Indigenous HealthInfoNet. Review of the Impact of Housing and Health-related Infrastructure on Indigenous Health [Internet]. Perth (AUST): Edith Cowan University Australian Indigenous Health InfoNet; 2008 [cited 2013 Oct 15]. Available from: http://www. healthinfonet.ecu.edu.au/determinants/physicalenvironment/reviews/our-review 21. PathWest Laboratory Medicine Western Australia. Online Test Directory. Perth (AUST): State Government of Western Australia; 2012. 22. Van Kerkhove MD, Vandemaele KA, Shinde V, JaramilloGutierrez G, Koukounari A, Donnelly CA, et al. Risk factors for severe outcomes following 2009 influenza A (H1N1) infection: a global pooled analysis. PLoS Med. 2011;8(7):e1001053. 23. Rothberg M, Haessler S, Brown R. Complications of Viral Influenza. Am J Med. 2008;121(4):258-64. 24. Health Protection Surveillance Centre. Enhanced Surveillance Form for Confirmed Hospitalised Influenza Cases Aged 0-14 Years. 1.9 ed. Dublin (IRL): Health Service Executive; 2012. 25. Centers for Disease Control and Prevention. Epi Info 7 [Internet]. Atlanta (GA): CDC; 2008 [cited 2013 Mar 18]. Available from: http://wwwn.cdc.gov/epiinfo/ 26. Communicable Disease Control Directorate. Notifiable Infectious Diseases Database. Notifiable Infectious Disease Reports. Perth (AUST): Western Australia Department of Health; 2013. 27. Massey PD, Miller A, Saggers S, Durrheim DN, Speare R, Taylor K, et al. Australian Aboriginal and Torres Strait Islander communities and the development of pandemic influenza containment strategies: Community voices and community control. Health Policy. 2011;103(2–3):184-90.
20
28. Western Australia Country Health Service. Kimberley Health Profile. Perth (AUST): State Government of Western Australia; 2012. 29. Van Kerkhove M, Hirve S, Koukounari A, Mounts A. Estimating Age-Specific Cumulative Incidence for the 2009 Influenza Pandemic: A Meta-Analysis of A(H1N1) pdm09 Serological Studies from 19 countries. Influenza Other Respir Viruses. 2013;7(5):872–86. 30. Janjua NZ, Skowronski DM, Hottes TS, Osei W, Adams E, Petric M, et al. Transmission dynamics and risk factors for pandemic H1N1-related illness: Outbreak investigation in a rural community of British Columbia, Canada. Influenza Other Respir Viruses. 2012;6(3):e54-e62. PubMed PMID: 22385647 31. Chang Y-S, vanHal SJ, Spencer PM, Gosbell IB, Collett PW. Comparison of adult patients hospitalised with pandemic (H1N1) 2009 influenza and seasonal influenza during the“PROTECT”phase of the pandemic response. Med J Aust. 2010;192(2):90-3. 32. Denholm JT, Gordon CL, Johnson PD, Hewagam SS, Stuart RL, Aboltins C, et al. Hospitalised adult patients with pandemic (H1N1) 2009 influenza in Melbourne, Australia. Med J Aust. 2010;192(2):84-6. 33. Haysom L, Williams R, Hodson EM, Lopez-Vargas PA, Roy LP, Lyle DM, et al. Natural history of chronic kidney disease in Australian Indigenous and non-Indigenous children: A 4-year population-based follow-up study. Med J Aust. 2009;190(6):303-6. 34. Menzies R, Turnour C, Chiu C, McIntyre P. Vaccine preventable diseases and vaccination coverage in Aboriginal and Torres Strait Islander people, Australia 2003 to 2006. Commun Dis Intell Q Rep. 2008;32 Suppl:S2-67.
35. Naidu L, Chiu C, Habig A, Lowbridge C, Jayasinghe S, Wang H, et al. Vaccine preventable diseases and vaccination coverage in Aboriginal and Torres Strait Islander people, Australia 2006-2010. Commun Dis Intell Q Rep. 2013;37 Suppl:S1-95. 36. Quinones-Parra S, Grant E, Loh L, Nguyen TH, Campbell KA, Tong SY, et al. Preexisting CD8+ T-cell immunity to the H7N9 influenza A virus varies across ethnicities. Proc Natl Acad Sci U S A. 2014;111(3):1049-54. 37. Dockery AM, Colquhoun S. Mobility of Aboriginal and Torres Strait Islander People: A Literature Review. Cooperative Research Centre for Remote Economic Participation (CRC-REP) Working Paper CW004. Alice Springs (AUST): Ninti One Limited; 2012. 38. Arcavi L, Benowitz NL. Cigarette smoking and infection. Arch Intern Med. 2004;164(20):2206-16. 39. Miller A, Durrheim AD. Aboriginal and Torres Strait Islander communities forgotten in new Australian National Action Plan for Human Influenza Pandemic: “Ask us, listen to us, share with us”. Med J Aust. 2010;193(6):316-7. 40. Lowen AC, Mubareka S, Steel J, Palese P. Influenza virus transmission is dependent on relative humidity and temperature. PLoS Pathog. 2007;3(10):1470-6.
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