Vol. 8 No. 1 Printed in Great Britain
International Journal of Epidemiology © Oxford University Press 1979
Teaching
GUY J LAVOIPIERRE 1 Lavoipierre G J (World Health Organization, Geneva, Switzerland). Epidemic investigation simulation. International Journal of Epidemiology 1979, 8: 00—00.
INTRODUCTION
It is axiomatic to state that the best learning experience in epidemiology — and in almost any walk of life for that matter — is through real problem solving activities. The selected problems should correspond to the reality of community situations. In fact, this is what all curricula and their corresponding learning objectives should strive to achieve, in providing trainees with the required principles and methods and having them applied in simulated exercises or through investigations conducted at large in the community. One of the skills an epidemiologist trainee should acquire is how to investigate outbreaks and epidemics. It is very seldom, if ever, that a group of trainees can investigate within the framework of a learning programme an outbreak actually occurring in a neighbouring community, district or town, and thereby put into practice their newly acquired methods and techniques. The only useful alternative is to simulate an outbreak/epidemic investigation and have it completed in a classroom situation. Recently, Wyatt (1) described such a simulation exercise in an issue of the International Journal of Epidemiology. The present article describes another simulation exercise which makes use of a different approach. As was rightly remarked by Wyatt, mistakes are made during actual investigations but they can often — but not always — be corrected either through consultation of books or with colleagues. The exercise described in this paper makes use of the simulation techniques described by Christine McGuire et al (4, 5) and Miller and Fullop (6). In World Health Organization, Geneva, Switzerland. A complete set of exercises are available from G J Lavoipierre.
particular, the following guiding principles were adhered to in its design: (a) it should be based on an actual outbreak; (b) it should be feasible to complete the exercise within a day's work (or 2 half-days as the case may be); (c) facts, figures and information in general provided to trainees should be as close as possible to the format in which they would be obtained in a real situation; (d) there should be several paths leading to an answer, if this is the case in real life; (e) obtaining the correct answer should, by design, require the trainees to go through a sequence of decision-making and the application of some of the techniques they have learned earlier in the course; (0 a general review of the exercise, including the way to go about things and why, should be undertaken by the trainees, comparing approaches and results under the guidance of an instructor. CONTENT OF EXERCISE The exercise* is based on a cholera outbreak which occurred on the island of Guam in July 1974 and was fully investigated by a team from the US Centre for Disease Control, Atlanta (3). It was the first time tha't cholera had ever been diagnosed and reported on the island. In spite of thorough and well-conducted epidemiological investigations, backed by solid laboratory investigations, the CDC team called in to assist the local public health specialists was unable to trace with certainty the * A second exercise, built around an hepatitis outbreak (2) has also been designed.
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Epidemic Investigation Simulation
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CONDUCT OF EXERCISE The exercise is divided into 5 steps, some of which the trainee may deliberately choose to ignore depending on his/her findings and analysis. These steps are the following: Step 1 —Official contacts and preliminary inforinformation collection Step 2 —Selection of course of action Step 3 —Diagnosis verification and confirmation of existence of an outbreak Step 4 —Looking for a common factor between cases Step 5 — Epidemiological investigations to test hypothesis formulated to explain outbreak and proposed control measures (if any). (An illustration of one of these 5 steps is presented in Annex 1). The trainee is informed that the options (or choices) offered in the exercise fall into one of the following 5 categories, so as to guide his decisions: 1. Clearly indicated and important to do so in this situation and at this stage of the investigation (score value+8); 2. Clearly indicated and should be done but of a more routine nature and of no special significance in this situation and at this stage of the investigation (score value +4); 3. Optional because the probability that the option/choice will be helpful is remote in this situation and at this stage of the investigation (score value 0); 4. Not indicated in this situation and at this stage of the investigation (score value —4); 5. Contra-indicated and/or harmful in this situation and at this stage of the investigation (score value —8).
Trainees are thus informed that the selection of contra-indicated options — even if they are correct short cuts and intuitive guesses — will influence their results negatively. For the first two steps the trainees are provided with 5 alternatives and are invited to choose one. For each of the last 3 steps, a series of 15 to 23 items for action (depending on the step) are presented. The trainee is free to choose as many items as he/she considers appropriate. Having chosen the items, the trainee erases the corresponding number of the answer sheet (by scratching or rubbing with an appropriate solvent) and is either directed to an envelope or given the answer immediately. Having analyzed the information collected, the trainee is now invited to choose one of 5 alternatives each of which will direct him/her to the next step. Whatever the pathway followed the trainee will always end up with a choice indicating clearly that the exercise is completed. Depending on the pathway that was followed, he/she is invited to draft a report outlining one of the following: a plan of action to control the outbreak; a new hypothesis and the various additional investigations required to verify its relevance; the most likely source of infection, the mode of transmission and recommended control measures. Finally completed answer sheets are collected and scoring is conducted in the following manner: (a) each of the trainee's (or group of trainee's) choices is given the value corresponding to the scores selected by a criterion group of experts who weighted all the choices of both exercises; (b) the algebraic sum of the positive and negative weights of the selected items is calculated and the total divided by the maximum possible scores which could be obtained by an optional pathway (ie exclusive and complete selection of items with a positive weight). This figure, reported as a percentage, is known as the Proficiency Score or the percentage agreement with the criterion group of experts in selecting procedures which the latter regard as clearly indicated and avoiding those they classify as contra-indicated; (c) finally, the percentage of the trainee's (or group of trainees') choices which have a positive weight is calculated and is recorded as the Efficiency Score. DISCUSSION This exercise and the second one mentioned earlier
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source of the outbreak: at best, a dish of raw salted fish was highly suspect as the probable source of infection. The exercise is made up of 32 documents: a text prepared by Dr Frank L Bryan (Bureau of Training, CDC, Atlanta) describing in detail the technique of investigations as applied to food-borne disease outbreaks (7); an introductory document setting out the problem, the trainee's role, and proposing 10 alternatives for the first 2 steps to be taken by the investigators; a series of 29 working papers (some very brief, others made up of several pages) providing either alternatives for decision-making, information and/or raw data; and finally an answer sheet. The 29 working papers are each placed in a sealed and clearly labelled envelope.
EPIDEMIC INVESTIGATION SIMULATION
Methodology illustrated Besides the obvious skills of reasoning and deduction from facts, these exercises arc meant to illustrate (and teach) the following points of methodology: — Technique of epidemiological investigation, in particular: team work approach with full participation of local medical authorities; necessity of diagnosis verification; necessity of well-documented facts to support conclusions because of economic and political constraints. — Construction of a bar diagram and a histogram from raw data (Docs 13 and 22). — Graphic presentation of raw data (Doc 18). — Identification of poisonous/contaminated foods (Docs 15 and 19). — Tabulation of data (Docs 9, 16, 17, 18 and 19).
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- Test of X1 (Doc 8). RESULTS
In general, the results have shown a need for the sort of training provided in the exercise. The ideal pathway has been rarely selected whereas a reasonably satisfactory approach is usually adopted by some 50% of trainees. One of the most common shortcomings, probably inherent to simulation situations such as these, is that although trainees are able to make the right hypothesis and to guess the source of the infection and the mode of transmission, they tend to choose few options which will allow them to prove their point and in particular, neglect the research of negative proofs to eliminate alternative hypotheses. The tendency is to jump to conclusions. Scoring of the exercises was initially performed and reviewed with the first generations of trainees but was not maintained later on because it is relatively time-consuming; as these exercises were usually performed in the framework of a 'guest training session' and not included by course directors in their official examination-evaluation system it was felt that the time thus taken for discussing scores was not fully justified. From the limited number of analyses performed various patterns of responses have been identified. Some trainees, for example, chose options which corresponded closely with those of the criterion group (ie they avoided most options classified as contra-indicated and selected most procedures favoured by the criterion group). These trainees ended up with moderate to high Efficiency and Proficiency scores with few errors of either omission (non-selection of a procedure with a positive weight) or commission (selection of a procedure with a negative weight). Other trainees had a constricted approach: they had high Efficiency scores (and therefore few errors of commission), moderate to low Proficiency scores with many errors of omission. A third pattern was the shot-gun approach characterized by a low Efficiency score, a moderate to low Proficiency score, usually combined with a few errors of omission but with many errors of commission. These were trainees who wanted to make sure they would be 'covered on all sides' forgetting that some procedures are not only useless but also counterproductive. When performed, scoring has shown that the second and third patterns (and -^riants thereof) were more frequently observed than the first one.
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have been used exclusively with trainees preparing for a post-graduate degree in epidemiology, cither at the Brussels Free University or within the WHOsponsored international training courses in epidemiology organized jointly and successively in Moscow, Prague, Alexandria (English-speaking) and Paris, Bobo-Dioulasso, Abidjan (French-speaking). Usually they were administered either half-way or towards the end of the training programme, being intended to allow teaching staff and trainees to verify the latter's understanding of epidemiological principles and methods, in addition to providing an extra opportunity for revision. Initially, trainees were invited to work individually on the exercise. Experience led us to group trainees in clusters of 3 or 4, preferably interdisciplinary when one had to deal with an heterogenous group (e.g. nurse, statistician, medical doctor, veterinarian). This led to a much more active and stimulating participation of all, besides being more in accordance with real life situations where epidemics are usually investigated by a team and rarely, if ever, by an individual. In any case, trainees were always invited to consult any number of books, lecture notebooks and laboratory notes as the need was felt. During the decade 1967-77 a total of 150 trainees completed the exercise, which has proved to be quite popular. In post-training evaluation organized by WHO during the last five years, the simulation exercises were always mentioned as a very useful learning technique and one which had the added advantage of grouping in a single activity a good deal of what epidemiologists should be called upon to practice.
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Step 1 — Official contacts and preliminary collection of information The most commonly observed failing on the part of trainees is a tendency to ignore this important step and either to proceed right away with the elucidation of some specific point related to the epidemic (but of less importance at such a preliminary stage of the investigation), or consider it simply as a formal act of 'political courtesy'.
Step 3 — Diagnosis verification and confirmation of existence of an outbreak Errors of omission are the main difficulties encountered by trainees at this stage. Existing data already collected and easy to collate, such as a quick review of hospital records to verify the presence/absence of an excessive number of diarrhoeal illnesses over and above the usual, a check on prescriptions and another on stool cultures are items rarely selected. Similarly trainees will seldom take the trouble of actually preparing a frequency distribution table of symptoms (when they have chosen to review hospital records) and compare this with the current distribution observed in the suspected disease (in this instance cholera); nor is the X2 test actually performed on data collected by means of a retrospective survey as should normally be done if this option is chosen. A minority of trainees, on the basis of data obtained and analyzed during that step of the exercise, are inclined to propose immediate control measures, such as mass vaccination and/or disinfection of all sources of water supply. Cholera still seems to have this effect on some. The largest number tend to formulate hypotheses and consequently bypass Step 4. It is seldom more than 25 to 30% of trainees who wisely decide to identify a common factor between cases before proposing hypotheses to explain the outbreak. It should be pointed out that with the recent
Step 4 — Looking for a common factor between cases This is undoubtedly the step where the greatest variation between one group of trainees and another has been observed. In general, trainees show an erratic, almost random distribution in their selection of options. It is at this stage of the investigation that the greatest errors of judgement are most frequently evidenced, as if trainees did not really know what they were after. For example, blood is collected for vibriocidal titer assays from matched age-sex controls, or unnecessary random sampling and interviews are conducted. A minority of trainees in some groups (maybe 15 to 20%) stop their investigations at this stage, making the error of confusing the discovery of a common factor between cases as proof of transmission without bringing the necessary documented evidence without which control measures will be difficult to enforce. Step 5 —Hypothesis testing and selection of control measures For obvious reasons the least number of errors are made in this step because trainees who undertake it have in general a good idea of what they are trying to prove. Except in two instances, the clear and detailed reports called for by 4 of the last 5 alternative decisions a trainee is invited to make, and intended to show the logical reasoning throughout the investigation, have always been incomplete and/or of poor quality. C. General Review During the general discussion which follows the review of the exercise by the instructor, the selflearning effect becomes evident. Spokesmen of a group of trainees or individual trainees are invited to explain the rationale behind their decisions, right or wrong, because it is easier for trainees to accept valid corrections when proposed by their colleagues. Individual and group involvement arc such that the role of the instructor is mainly one of facilitating the discussions, pointing out errors of omission and helping participants to identify all the lessons and principles taught by the exercises. CONCLUSION Unlike the exercise described by Wyatt, these 2 simulation exercises are not self-correcting in the
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Step 2 — Selection of course of action The usual mistake is to accept the premises upon which the investigators were invited to solve the epidemic problems and to assume that the diagnoses were correct and an epidemic situation existed. The selection of a course of action that would lead to Step 3 is by-passed by a good third of the trainees. Nevertheless, the Guam outbreak investigation is quite revealing in the sense that the American investigators took the trouble of sending specimens across the Pacific Ocean to the Communicable Disease Centre (CDC) laboratories in Atlanta to have the diagnosis confirmed.
(1977) addition of Bryan's paper to the exercise, the proportion of trainees selecting Step 4 has been closer to the 50% mark.
EPIDEMIC INVESTIGATION SIMULATION
ANNEX 1 Simulation Exercise. Investigation of an outbreak of gastro-intestinal illness. Step no. 3 Having decided to verify the diagnosis of identified cases and confirm the existence of an outbreak, you would now: (CHOOSE AS MANY ITEMS AS YOU CONSIDER APPROPRIATE AT THIS STAGE OF YOUR INVESTIGATION) 11. Conduct further investigations among a random sample of Guam population to obtain additional information on diarrhocal episodes between 15-21 July 1974. 12. Collect rectal swabs from the 5 other workers who had experienced a diarrhoeal illness for purposes of bacteriological isolation (V cholerae and S typbi). 13. Collect rectal swabs from all workers of the Harmon construction company for purposes of bacteriological isolation (V cholerae and 5 typbi). 14. Interview the Harmon construction company manager to verify the presence/absence of additional diarrhoeal illnesses among other personnel employed by his company. 15. Conduct a rapid telephone interview of all Guam physicians to ascertain the presence/ absence of additional cholera-like diarrhoeal illness. 16. Collect blood specimens from the 5 coworkers of the index case to check by blood culture for presence/absence of 5 typhi. 17. Collect blood specimens from all workers of the construction company which employed the index case to check by blood culture for
presence/absence of S typbi Send bacteriological colonies isolated from index case to Communicable Disease Center Laboratory in Atlanta to confirm identification of V cholerae made by Guam Public Health Laboratory. 19. Review the records of the Civilian Hospital where the index case died to identify presence/ absence of additional cholera-like diarrhoeal illness among patients who visited the Outpatients Department during the period July 15-July 25, 1974. 20. Visit US Naval Hospital to identify presence/ absence of additional cholera-like diarrhoeal illness among patients hospitalized during the month of July. 21. Organize, on a random-sample basis, a houseto-house survey among the community where the cases lived to identify individuals who displayed symptoms of gastro-enteritis during the previous 2 weeks. 22. Check the number of prescriptions for antidiarrhoeic drugs (Lomotil, Paregoric, Donnagcl) filled by 5 Guam pharmacies between February—July 1974. 23. Review the number of stool cultures obtained at the Civilian Hospital laboratory in July 1974. 24. Review the number of persons visiting the outpatient department at the Civilian Hospital, Naval Hospital and Air Force Clinic for diarrhocal illness between mid-June and beginning August 1974. 25. Interview the 54 Harmon construction company workers and the personnel occupying buildings 2 and 3 (Harmon construction site) concerning diarrhoeal illness experienced in July by them or members of their family (date of onset and duration). Having analyzed the information you have obtained, you would now: (CHOOSE ONE OF THE ALTERNATIVES) 26. (A) Conclude your investigations and submit a report of your findings to the Guam Department of Public Health Services and to the Director, C D C , Atlanta, indicating the measures you recommend to prevent the recurrence of similar outbreaks. 26. (B) Widen your investigation to relate the outbreak to time, place and person and look for a common factor among cases. 26. (C) Recommend to the Guam Department of Public Health Services the immediate implementation of a mass immunization 18.
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sense that the trainee can proceed through all the steps without having necessarily completed one part. His/her achievements will depend on the correct application of methods previously learned in the course and a wrong decision will be sanctioned by the selection of an unsatisfactory investigation pathway. Two criticisms could be justly aimed at this teaching/learning technique: it is rather timeconsuming to prepare the required material and it is somewhat lengthy to perform. These however are outweighed by the enthusiastic participation of trainees and by the fact that the exercise is also an investment as it can be used repeatedly, thus allowing costly teacher's time to be used more efficiently in helping trainees during the learning process.
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of Epidemiology 6i 173, 1977. (2) Mason J O and McLean W R. Infectious hepatitis outbreak associated with oysters. American Journal of Hygiene 75. I l l , 1962. (3)Merson M H et al. Cholera in Guam. Unpublished report Bacterial Diseases Division, Center for Disease Control, Atlanta, USA. 1975. (4) McGuire Christine H and Solomon Lawrence H. Clinical simulations. Appleton Century Croft, New York, 1971. (5) McGuire Christine H et al. Construction and use of written simulations. Psychological Corporation, 757 Third Avenue, New York 10017. ^ (6) Miller George F and Fulop Tomas. Educational strategies for the Health Professions. WHO Public Papers, No. 61. (7) Bryan Frank L. Investigation of foodborne disease outbreaks. Centre for Disease Control. Training Programme, Atlanta, Georgia 30333. USA.
(Revised version received 18 September 1978)
Mortality Data Available on Computer Tape Transcripts WHO is making available for public use a number of standardized computer tape transcripts of mortality data from the Organization's data bank file. This service is in response to the need for recent information in a form (or with details) not usually provided in the data published regularly in World Health
Statistics Annual or in World Health Statistics Quarterly. Further information (in English and French) on this service will be found in World Health Statistics Annual, Vol 1, 1978, Annex II (Users' guide to standardized computer tape transcripts), pp 5 32-5 38.
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campaign combined with prophylactic treatment of contacts in order to prevent the extension of the outbreak and continue your investigations. 26. (D) Plan and conduct detailed epidemiological investigations to test the hypothesis you have formulated to explain the most likely source of infection and the mode of transmission. 26. (E) Conclude your investigations, submit a report of your findings to the Guam Department of Public Health Services and the Director, C D C , Atlanta, and offer assistance to Dr Angeles and his staff in undertaking the control measures you recommend. REFERENCES (1) Wyatt H V. Investigating an Epidemic: A Seven Part
International Journal of Epidemiology © Oxford University Press 1979
Teaching
GUY J LAVOIPIERRE 1 Lavoipierre G J (World Health Organization, Geneva, Switzerland). Epidemic investigation simulation. International Journal of Epidemiology 1979, 8: 00—00.
INTRODUCTION
It is axiomatic to state that the best learning experience in epidemiology — and in almost any walk of life for that matter — is through real problem solving activities. The selected problems should correspond to the reality of community situations. In fact, this is what all curricula and their corresponding learning objectives should strive to achieve, in providing trainees with the required principles and methods and having them applied in simulated exercises or through investigations conducted at large in the community. One of the skills an epidemiologist trainee should acquire is how to investigate outbreaks and epidemics. It is very seldom, if ever, that a group of trainees can investigate within the framework of a learning programme an outbreak actually occurring in a neighbouring community, district or town, and thereby put into practice their newly acquired methods and techniques. The only useful alternative is to simulate an outbreak/epidemic investigation and have it completed in a classroom situation. Recently, Wyatt (1) described such a simulation exercise in an issue of the International Journal of Epidemiology. The present article describes another simulation exercise which makes use of a different approach. As was rightly remarked by Wyatt, mistakes are made during actual investigations but they can often — but not always — be corrected either through consultation of books or with colleagues. The exercise described in this paper makes use of the simulation techniques described by Christine McGuire et al (4, 5) and Miller and Fullop (6). In World Health Organization, Geneva, Switzerland. A complete set of exercises are available from G J Lavoipierre.
particular, the following guiding principles were adhered to in its design: (a) it should be based on an actual outbreak; (b) it should be feasible to complete the exercise within a day's work (or 2 half-days as the case may be); (c) facts, figures and information in general provided to trainees should be as close as possible to the format in which they would be obtained in a real situation; (d) there should be several paths leading to an answer, if this is the case in real life; (e) obtaining the correct answer should, by design, require the trainees to go through a sequence of decision-making and the application of some of the techniques they have learned earlier in the course; (0 a general review of the exercise, including the way to go about things and why, should be undertaken by the trainees, comparing approaches and results under the guidance of an instructor. CONTENT OF EXERCISE The exercise* is based on a cholera outbreak which occurred on the island of Guam in July 1974 and was fully investigated by a team from the US Centre for Disease Control, Atlanta (3). It was the first time tha't cholera had ever been diagnosed and reported on the island. In spite of thorough and well-conducted epidemiological investigations, backed by solid laboratory investigations, the CDC team called in to assist the local public health specialists was unable to trace with certainty the * A second exercise, built around an hepatitis outbreak (2) has also been designed.
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Epidemic Investigation Simulation
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CONDUCT OF EXERCISE The exercise is divided into 5 steps, some of which the trainee may deliberately choose to ignore depending on his/her findings and analysis. These steps are the following: Step 1 —Official contacts and preliminary inforinformation collection Step 2 —Selection of course of action Step 3 —Diagnosis verification and confirmation of existence of an outbreak Step 4 —Looking for a common factor between cases Step 5 — Epidemiological investigations to test hypothesis formulated to explain outbreak and proposed control measures (if any). (An illustration of one of these 5 steps is presented in Annex 1). The trainee is informed that the options (or choices) offered in the exercise fall into one of the following 5 categories, so as to guide his decisions: 1. Clearly indicated and important to do so in this situation and at this stage of the investigation (score value+8); 2. Clearly indicated and should be done but of a more routine nature and of no special significance in this situation and at this stage of the investigation (score value +4); 3. Optional because the probability that the option/choice will be helpful is remote in this situation and at this stage of the investigation (score value 0); 4. Not indicated in this situation and at this stage of the investigation (score value —4); 5. Contra-indicated and/or harmful in this situation and at this stage of the investigation (score value —8).
Trainees are thus informed that the selection of contra-indicated options — even if they are correct short cuts and intuitive guesses — will influence their results negatively. For the first two steps the trainees are provided with 5 alternatives and are invited to choose one. For each of the last 3 steps, a series of 15 to 23 items for action (depending on the step) are presented. The trainee is free to choose as many items as he/she considers appropriate. Having chosen the items, the trainee erases the corresponding number of the answer sheet (by scratching or rubbing with an appropriate solvent) and is either directed to an envelope or given the answer immediately. Having analyzed the information collected, the trainee is now invited to choose one of 5 alternatives each of which will direct him/her to the next step. Whatever the pathway followed the trainee will always end up with a choice indicating clearly that the exercise is completed. Depending on the pathway that was followed, he/she is invited to draft a report outlining one of the following: a plan of action to control the outbreak; a new hypothesis and the various additional investigations required to verify its relevance; the most likely source of infection, the mode of transmission and recommended control measures. Finally completed answer sheets are collected and scoring is conducted in the following manner: (a) each of the trainee's (or group of trainee's) choices is given the value corresponding to the scores selected by a criterion group of experts who weighted all the choices of both exercises; (b) the algebraic sum of the positive and negative weights of the selected items is calculated and the total divided by the maximum possible scores which could be obtained by an optional pathway (ie exclusive and complete selection of items with a positive weight). This figure, reported as a percentage, is known as the Proficiency Score or the percentage agreement with the criterion group of experts in selecting procedures which the latter regard as clearly indicated and avoiding those they classify as contra-indicated; (c) finally, the percentage of the trainee's (or group of trainees') choices which have a positive weight is calculated and is recorded as the Efficiency Score. DISCUSSION This exercise and the second one mentioned earlier
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source of the outbreak: at best, a dish of raw salted fish was highly suspect as the probable source of infection. The exercise is made up of 32 documents: a text prepared by Dr Frank L Bryan (Bureau of Training, CDC, Atlanta) describing in detail the technique of investigations as applied to food-borne disease outbreaks (7); an introductory document setting out the problem, the trainee's role, and proposing 10 alternatives for the first 2 steps to be taken by the investigators; a series of 29 working papers (some very brief, others made up of several pages) providing either alternatives for decision-making, information and/or raw data; and finally an answer sheet. The 29 working papers are each placed in a sealed and clearly labelled envelope.
EPIDEMIC INVESTIGATION SIMULATION
Methodology illustrated Besides the obvious skills of reasoning and deduction from facts, these exercises arc meant to illustrate (and teach) the following points of methodology: — Technique of epidemiological investigation, in particular: team work approach with full participation of local medical authorities; necessity of diagnosis verification; necessity of well-documented facts to support conclusions because of economic and political constraints. — Construction of a bar diagram and a histogram from raw data (Docs 13 and 22). — Graphic presentation of raw data (Doc 18). — Identification of poisonous/contaminated foods (Docs 15 and 19). — Tabulation of data (Docs 9, 16, 17, 18 and 19).
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- Test of X1 (Doc 8). RESULTS
In general, the results have shown a need for the sort of training provided in the exercise. The ideal pathway has been rarely selected whereas a reasonably satisfactory approach is usually adopted by some 50% of trainees. One of the most common shortcomings, probably inherent to simulation situations such as these, is that although trainees are able to make the right hypothesis and to guess the source of the infection and the mode of transmission, they tend to choose few options which will allow them to prove their point and in particular, neglect the research of negative proofs to eliminate alternative hypotheses. The tendency is to jump to conclusions. Scoring of the exercises was initially performed and reviewed with the first generations of trainees but was not maintained later on because it is relatively time-consuming; as these exercises were usually performed in the framework of a 'guest training session' and not included by course directors in their official examination-evaluation system it was felt that the time thus taken for discussing scores was not fully justified. From the limited number of analyses performed various patterns of responses have been identified. Some trainees, for example, chose options which corresponded closely with those of the criterion group (ie they avoided most options classified as contra-indicated and selected most procedures favoured by the criterion group). These trainees ended up with moderate to high Efficiency and Proficiency scores with few errors of either omission (non-selection of a procedure with a positive weight) or commission (selection of a procedure with a negative weight). Other trainees had a constricted approach: they had high Efficiency scores (and therefore few errors of commission), moderate to low Proficiency scores with many errors of omission. A third pattern was the shot-gun approach characterized by a low Efficiency score, a moderate to low Proficiency score, usually combined with a few errors of omission but with many errors of commission. These were trainees who wanted to make sure they would be 'covered on all sides' forgetting that some procedures are not only useless but also counterproductive. When performed, scoring has shown that the second and third patterns (and -^riants thereof) were more frequently observed than the first one.
Downloaded from http://ije.oxfordjournals.org/ at University of Bath Library & Learning Centre on June 11, 2015
have been used exclusively with trainees preparing for a post-graduate degree in epidemiology, cither at the Brussels Free University or within the WHOsponsored international training courses in epidemiology organized jointly and successively in Moscow, Prague, Alexandria (English-speaking) and Paris, Bobo-Dioulasso, Abidjan (French-speaking). Usually they were administered either half-way or towards the end of the training programme, being intended to allow teaching staff and trainees to verify the latter's understanding of epidemiological principles and methods, in addition to providing an extra opportunity for revision. Initially, trainees were invited to work individually on the exercise. Experience led us to group trainees in clusters of 3 or 4, preferably interdisciplinary when one had to deal with an heterogenous group (e.g. nurse, statistician, medical doctor, veterinarian). This led to a much more active and stimulating participation of all, besides being more in accordance with real life situations where epidemics are usually investigated by a team and rarely, if ever, by an individual. In any case, trainees were always invited to consult any number of books, lecture notebooks and laboratory notes as the need was felt. During the decade 1967-77 a total of 150 trainees completed the exercise, which has proved to be quite popular. In post-training evaluation organized by WHO during the last five years, the simulation exercises were always mentioned as a very useful learning technique and one which had the added advantage of grouping in a single activity a good deal of what epidemiologists should be called upon to practice.
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Step 1 — Official contacts and preliminary collection of information The most commonly observed failing on the part of trainees is a tendency to ignore this important step and either to proceed right away with the elucidation of some specific point related to the epidemic (but of less importance at such a preliminary stage of the investigation), or consider it simply as a formal act of 'political courtesy'.
Step 3 — Diagnosis verification and confirmation of existence of an outbreak Errors of omission are the main difficulties encountered by trainees at this stage. Existing data already collected and easy to collate, such as a quick review of hospital records to verify the presence/absence of an excessive number of diarrhoeal illnesses over and above the usual, a check on prescriptions and another on stool cultures are items rarely selected. Similarly trainees will seldom take the trouble of actually preparing a frequency distribution table of symptoms (when they have chosen to review hospital records) and compare this with the current distribution observed in the suspected disease (in this instance cholera); nor is the X2 test actually performed on data collected by means of a retrospective survey as should normally be done if this option is chosen. A minority of trainees, on the basis of data obtained and analyzed during that step of the exercise, are inclined to propose immediate control measures, such as mass vaccination and/or disinfection of all sources of water supply. Cholera still seems to have this effect on some. The largest number tend to formulate hypotheses and consequently bypass Step 4. It is seldom more than 25 to 30% of trainees who wisely decide to identify a common factor between cases before proposing hypotheses to explain the outbreak. It should be pointed out that with the recent
Step 4 — Looking for a common factor between cases This is undoubtedly the step where the greatest variation between one group of trainees and another has been observed. In general, trainees show an erratic, almost random distribution in their selection of options. It is at this stage of the investigation that the greatest errors of judgement are most frequently evidenced, as if trainees did not really know what they were after. For example, blood is collected for vibriocidal titer assays from matched age-sex controls, or unnecessary random sampling and interviews are conducted. A minority of trainees in some groups (maybe 15 to 20%) stop their investigations at this stage, making the error of confusing the discovery of a common factor between cases as proof of transmission without bringing the necessary documented evidence without which control measures will be difficult to enforce. Step 5 —Hypothesis testing and selection of control measures For obvious reasons the least number of errors are made in this step because trainees who undertake it have in general a good idea of what they are trying to prove. Except in two instances, the clear and detailed reports called for by 4 of the last 5 alternative decisions a trainee is invited to make, and intended to show the logical reasoning throughout the investigation, have always been incomplete and/or of poor quality. C. General Review During the general discussion which follows the review of the exercise by the instructor, the selflearning effect becomes evident. Spokesmen of a group of trainees or individual trainees are invited to explain the rationale behind their decisions, right or wrong, because it is easier for trainees to accept valid corrections when proposed by their colleagues. Individual and group involvement arc such that the role of the instructor is mainly one of facilitating the discussions, pointing out errors of omission and helping participants to identify all the lessons and principles taught by the exercises. CONCLUSION Unlike the exercise described by Wyatt, these 2 simulation exercises are not self-correcting in the
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Step 2 — Selection of course of action The usual mistake is to accept the premises upon which the investigators were invited to solve the epidemic problems and to assume that the diagnoses were correct and an epidemic situation existed. The selection of a course of action that would lead to Step 3 is by-passed by a good third of the trainees. Nevertheless, the Guam outbreak investigation is quite revealing in the sense that the American investigators took the trouble of sending specimens across the Pacific Ocean to the Communicable Disease Centre (CDC) laboratories in Atlanta to have the diagnosis confirmed.
(1977) addition of Bryan's paper to the exercise, the proportion of trainees selecting Step 4 has been closer to the 50% mark.
EPIDEMIC INVESTIGATION SIMULATION
ANNEX 1 Simulation Exercise. Investigation of an outbreak of gastro-intestinal illness. Step no. 3 Having decided to verify the diagnosis of identified cases and confirm the existence of an outbreak, you would now: (CHOOSE AS MANY ITEMS AS YOU CONSIDER APPROPRIATE AT THIS STAGE OF YOUR INVESTIGATION) 11. Conduct further investigations among a random sample of Guam population to obtain additional information on diarrhocal episodes between 15-21 July 1974. 12. Collect rectal swabs from the 5 other workers who had experienced a diarrhoeal illness for purposes of bacteriological isolation (V cholerae and S typbi). 13. Collect rectal swabs from all workers of the Harmon construction company for purposes of bacteriological isolation (V cholerae and 5 typbi). 14. Interview the Harmon construction company manager to verify the presence/absence of additional diarrhoeal illnesses among other personnel employed by his company. 15. Conduct a rapid telephone interview of all Guam physicians to ascertain the presence/ absence of additional cholera-like diarrhoeal illness. 16. Collect blood specimens from the 5 coworkers of the index case to check by blood culture for presence/absence of 5 typhi. 17. Collect blood specimens from all workers of the construction company which employed the index case to check by blood culture for
presence/absence of S typbi Send bacteriological colonies isolated from index case to Communicable Disease Center Laboratory in Atlanta to confirm identification of V cholerae made by Guam Public Health Laboratory. 19. Review the records of the Civilian Hospital where the index case died to identify presence/ absence of additional cholera-like diarrhoeal illness among patients who visited the Outpatients Department during the period July 15-July 25, 1974. 20. Visit US Naval Hospital to identify presence/ absence of additional cholera-like diarrhoeal illness among patients hospitalized during the month of July. 21. Organize, on a random-sample basis, a houseto-house survey among the community where the cases lived to identify individuals who displayed symptoms of gastro-enteritis during the previous 2 weeks. 22. Check the number of prescriptions for antidiarrhoeic drugs (Lomotil, Paregoric, Donnagcl) filled by 5 Guam pharmacies between February—July 1974. 23. Review the number of stool cultures obtained at the Civilian Hospital laboratory in July 1974. 24. Review the number of persons visiting the outpatient department at the Civilian Hospital, Naval Hospital and Air Force Clinic for diarrhocal illness between mid-June and beginning August 1974. 25. Interview the 54 Harmon construction company workers and the personnel occupying buildings 2 and 3 (Harmon construction site) concerning diarrhoeal illness experienced in July by them or members of their family (date of onset and duration). Having analyzed the information you have obtained, you would now: (CHOOSE ONE OF THE ALTERNATIVES) 26. (A) Conclude your investigations and submit a report of your findings to the Guam Department of Public Health Services and to the Director, C D C , Atlanta, indicating the measures you recommend to prevent the recurrence of similar outbreaks. 26. (B) Widen your investigation to relate the outbreak to time, place and person and look for a common factor among cases. 26. (C) Recommend to the Guam Department of Public Health Services the immediate implementation of a mass immunization 18.
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sense that the trainee can proceed through all the steps without having necessarily completed one part. His/her achievements will depend on the correct application of methods previously learned in the course and a wrong decision will be sanctioned by the selection of an unsatisfactory investigation pathway. Two criticisms could be justly aimed at this teaching/learning technique: it is rather timeconsuming to prepare the required material and it is somewhat lengthy to perform. These however are outweighed by the enthusiastic participation of trainees and by the fact that the exercise is also an investment as it can be used repeatedly, thus allowing costly teacher's time to be used more efficiently in helping trainees during the learning process.
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INTERNATIONAL JOURNAL OF EPIDEMIOLOGY Simulation used in Teaching. International Journal
of Epidemiology 6i 173, 1977. (2) Mason J O and McLean W R. Infectious hepatitis outbreak associated with oysters. American Journal of Hygiene 75. I l l , 1962. (3)Merson M H et al. Cholera in Guam. Unpublished report Bacterial Diseases Division, Center for Disease Control, Atlanta, USA. 1975. (4) McGuire Christine H and Solomon Lawrence H. Clinical simulations. Appleton Century Croft, New York, 1971. (5) McGuire Christine H et al. Construction and use of written simulations. Psychological Corporation, 757 Third Avenue, New York 10017. ^ (6) Miller George F and Fulop Tomas. Educational strategies for the Health Professions. WHO Public Papers, No. 61. (7) Bryan Frank L. Investigation of foodborne disease outbreaks. Centre for Disease Control. Training Programme, Atlanta, Georgia 30333. USA.
(Revised version received 18 September 1978)
Mortality Data Available on Computer Tape Transcripts WHO is making available for public use a number of standardized computer tape transcripts of mortality data from the Organization's data bank file. This service is in response to the need for recent information in a form (or with details) not usually provided in the data published regularly in World Health
Statistics Annual or in World Health Statistics Quarterly. Further information (in English and French) on this service will be found in World Health Statistics Annual, Vol 1, 1978, Annex II (Users' guide to standardized computer tape transcripts), pp 5 32-5 38.
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campaign combined with prophylactic treatment of contacts in order to prevent the extension of the outbreak and continue your investigations. 26. (D) Plan and conduct detailed epidemiological investigations to test the hypothesis you have formulated to explain the most likely source of infection and the mode of transmission. 26. (E) Conclude your investigations, submit a report of your findings to the Guam Department of Public Health Services and the Director, C D C , Atlanta, and offer assistance to Dr Angeles and his staff in undertaking the control measures you recommend. REFERENCES (1) Wyatt H V. Investigating an Epidemic: A Seven Part
