Reviews in Medical Virology
Rev. Med. Virol. 2015; 25: 69–70. Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/rmv.1828
Ebola in West Africa: the end of the ﬁrst year
In retrospect, the ﬁrst case of Ebola in West Africa died at the end of December 2013, perhaps having acquired the infection from contact with free-tailed bats . The epidemic thus has been underway now for 12 months  which gives an opportunity for perspective and comparison with other viruses that have impinged on the consciousness of the general public in dramatic ways. To rank viral pathogens into tiers of importance, we need to consider how contagious they are, their mortality and options for intervention. Ebola virus was discovered in 1976 and named after “a small river in Zaire which ﬂows westward, north of Yambuku, the village of origin of the patient from whom the ﬁrst isolate was obtained” . We know from the reminiscences of pioneers who were involved in the investigation of that ﬁrst outbreak how to control Ebola . It requires contact tracing, isolation of patients with fever, rapid diagnosis, quarantine of those who turn out to have Ebola and safe burials. These interventions proved to be successful in all of the 10 rural Ebola outbreaks that occurred after 1976 [4,5]. Then, a year ago, Ebola took off in West African urban areas, with high population densities, poor infrastructure and populations wary of ofﬁcialdom. The local medical system was slow to diagnose the infection and only notiﬁed WHO in March 2014 . The international community was then very slow to react as the virus crossed international borders, leaving a medical charity, Médecins Sans Frontières, to cope with the dreadful practicalities. This illustrates the bravery of the health care workers who volunteered to work in dreadfully suboptimal conditions, 366 of whom have died so far (6). The virus has not evolved to become more contagious since 1976, because ﬁeld evaluations show that the basic reproductive number for Ebola has remained low (approximate range 1.7–2.2) in West Africa but has spread widely because it was not being contained effectively . Even a virus with a low basic reproductive number can become established in a community and move into an exponential phase of transmission if it is not curtailed by isolation of infected patients. For Copyright © 2015 John Wiley & Sons, Ltd.
example, HIV is not readily transmissible from person to person, and requires more intimate contact than does Ebola yet has established itself as a pandemic. More colloquially, once the genie is out of the bag, it can take a long time to put it back inside again. The organisational skills, logistics, resources and decisiveness required to achieve this control cry out for the military to be put in charge. The case fatality rate of Ebola is high; about 70% when calculated using cases with a deﬁnitive outcome, compared to about 40% when considering the 7588 deaths out of 19,497 cases reported on the WHO website [2,6]. The true rate is thus similar to that of H5N1 bird ﬂu, although only 393 deaths have been reported worldwide for that infection, despite the number of column inches devoted to reporting it over the last few years. The death rate in Ebola may be approximately twice that of smallpox, a disease whose high mortality and debilitating demise galvanised international efforts to coordinate global eradication of the causative virus. The other virus well on the way to eradication is polio which, among the minority of infected individuals who developed disease, had a case fatality rate of about 5% in children and 30% in adults. Thus, Ebola has killed many more people than has bird ﬂu and kills a higher proportion than either of the two viruses the world community has previously targeted for eradication. This implies that a strategic, international case could be made for preparing treatment and vaccine countermeasures in case Ebola ﬂares up again. However, Ebola kills far fewer people than does HIV, so these investments must be additional to those required to control the latter. Journalists often report that there is no treatment for Ebola. Certainly, there is no antidote that can be given to miraculously resurrect a moribund patient, but the same applies to most virus infections. Antiviral treatments aim to slow down the replication of a virus and minimise its major pathological effects in the expectation that the troops of the immune system will eventually ride to rescue the patient. Clinical interventions, which are routinely available
in developed countries, such as intravenous replacement of ﬂuid, correction of electrolyte imbalances and ventilation to reduce ﬂuid accumulation in the lungs, have undoubtedly reduced the case fatality rate of the small number of Ebola patients fortunate enough to have access to these. Another intervention that is powerful at the community level is quarantine; this dramatically terminated the SARS pandemic (which killed only 774 people despite its high media proﬁle) and should do so eventually for Ebola. Thus, the public should see Ebola as just the latest scourge to threaten the increasing number of REFERENCES
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humans who crowd our planet. There will be other virus outbreaks in the future and we should rejoice when international collaborations control each of these in turn. Despite the apocalyptic predictions in the popular press which accompany each new example, the bottom line is that there is not a single virus which has both high transmissibility between humans and a high mortality. P.D. Grifﬁths p.grifﬁ[email protected]
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Copyright © 2015 John Wiley & Sons, Ltd.
Rev. Med. Virol. 2015; 25: 69–70. DOI: 10.1002/rmv