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You are assigned to investigate an deadly outbreak occurring in Haiti. After reviewing the preliminary information, you know you have to work quickly and accurately to analyze the outbreak demographics in order to identify the disease pathogen and disease transmission methods. This is the only way you may be able to stop the outbreak and prevent more disease!


As an epidemiologist with the National Institutesaerial view of city building ruined by an earthquake of Health (NIH), you have worked on disease outbreaks all over the world.  When you got the call to help on an investigation of an outbreak in Haiti, you knew you and your team were headed for a particularly challenging case.

A recent earthquake devastated many areas in Haiti; a few large cities were particularly hard hit, but smaller towns and villages were also severely damaged. Lack of housing and proper sanitation procedures, unsafe water supplies, and inadequate medical treatment created numerous healthcare problems. You weren’t surprised when an outbreak of some kind occurred; these kinds of conditions are ideal for infectious disease outbreaks.

Medical personnel in Haiti have written a tentative list of possible diseases that may be the cause of this outbreak. Lack of proper lab equipment and supplies have prevented a final diagnosis. The outbreak has been going on for weeks and field personnel, limited Haitian medical teams, and international volunteers have been unable to control it. You and your team are bringing additional equipment, supplies, and expertise to analyze and contain the disease.

Narrowing down the possible diagnoses will certainly help your team identify the pathogen more quickly which will lead to finding disease transmission possibilities.   During the flight to Port-au-Prince, Haiti’s capital, and during the car ride to Mirebalais, your first stop, you review the information sent to you. You don’t want to waste any time once you get to the Mirebalais health facility.

Identifying the disease is critical not only for proper treatment but also for finding out how the disease is transmitted. Knowing the transmission method leads to prevention, containment, and control.  You and your team know you will need to work hard to end this outbreak.  Reports indicate that death can come within hours of onset of symptoms. You need to work quickly but accurately in order to save as many lives as possible.

Part I: Diagnosis
  You probably remember the Ebola outbreak in west Africa of 2014-2015. The outbreak was first diagnosed in some areas as malaria and in other areas as cholera. Prevention, containment, and treatment of patients were decided based on incorrect diagnoses. The outbreak spread rapidly and people died, partly due to incorrect treatment and partly because they had incorrectly identified how the disease was spread. People moved freely from village to village and even to different countries. (Ebola has a high mortality rate even if patients receive treatment.)

  1. Start the process of identifying the initial diagnosis by reviewing the symptoms that Haitian healthcare officials have observed. They have assembled a working case definition for the illness. In epidemiology, a case definition is a description of specific conditions and details that should be met in order for the person to be identified as having a particular disease or other health condition.

This step is critical to control of the outbreak.

Case definition:  Haiti outbreak

Following an incubation period of 6-48 hours, abrupt onset of massive diarrhea begins. Diarrhea has a milky appearance. Nausea and vomiting occur.

Because of the loss of fluids, dehydration may occur. Reduced urine output may result
from electrolyte imbalances and kidney failure follows. Seizure, coma, and cardiac arrest with death have occurred.

Loss of skin elasticity and muscle cramps are common.

  1. The Haitian Health Department also compiled a list of differential diagnoses for the symptoms for this outbreak disease. A differential diagnosis is an alternate diagnosis for symptoms presented in a disease or adverse health condition. Use the NIH site listed below to investigate each differential disease and as a team, decide on an initial diagnosis.

National Institutes of Health (NIH)  Medline Plus Medical Encyclopedia  https://www.nlm.nih.gov/medlineplus/encyclopedia.html

Differential Diagnoses for Haitian Outbreak      

1) E. coli infection
2) Cholera
3) Amebic dysentery
4) Giardiasis
5) Food poisoning
6) Ascariasis
7) Trichinosis
8) Leishmaniasis

Note the reason you eliminated a disease as a possible cause of this outbreak on the Reasoning for Possible Differential Diagnosis Elimination worksheet. For example, if the disease includes the presence of a rash and the outbreak disease does not include a rash, note the reason and eliminate that disease from the list.

Report your initial diagnosis and the reasons behind your choice as soon as possible. 

Test samples were sent to the laboratory at Port-au-Prince. When you receive lab reports, analyze the results and report a final diagnosis.   

Part II:  Analyzing the Data
In order to find out more about the cause of this disease, how the outbreak started, and its transmission method, review the data you received from the Haitian Health Ministry beginning with the locations of the cases during the first two weeks. Data is provided in both a data table and epi-curve. An epi-curve is a graph that plots the course of an outbreak by time of onset.

Towns and villages have already been grouped by Haitian public health officials as the outbreak seems to affect certain locations similarly. The town of Mirebalais is considered separately.


Community Group 1 includes the towns of:

  • L’Estere
  • Desdeunes
  • Grande
  • Saline
  • Dessalines
  • Marc
  • Desarmes

Community Group 2 includes the towns of:

  • Gonaive
  • Ennery
  • Plaisance
  • Saint-Michel-de-l’Attalaye
  • Port-au-Prince

Answer the following questions to help you in your analysis. 

  1. Where did the outbreak start?
  2. How long did it take to spread from the initial outbreak location to the next location?
  3. Where did the disease spread next?
  4. d) How long did it take to spread to that location?
  5. e) Where did the disease spread next?
  6. f) What happened to the number of cases in each location from Day 1 to Day 14? Using the data table and epi curve suggest a reason for the spread to each location. What are some possibilities for how the disease is being transmitted?
  1. Your team has just received updated data. The data provides new information that could lead to identifying the source of infection and containing the outbreak. Analyze the numbers and locations of cases and revise your hypothesis of the source of contamination, if necessary.

Analyze the new data and answer the following questions:  

  1. a) What is happening in Mirebalais? What do you think caused the change in number of cases?



  1. b) What is happening in Community 1? in Community 2? What do you think caused the change in number of cases?




  1. c) In light of this new data, revise your hypothesis, if necessary. What factors led you to make that hypothesis?



Part III:  Mapping the Outbreak

1. Begin your investigation of the initial source of this outbreak. Obtain maps of Haiti that show the locations of the outbreaks. Review the number and locations of the compiled case data.

You must refer to all three maps as you work through locations.

Remember that town and villages have been grouped as the outbreak seems to affect certain locations similarly. Mirebalais is considered separately.


Community Group 1 includes the towns of:

  • L’Estere
  • Desdeunes
  • Grande
  • Saline
  • Dessalines
  • Marc
  • Desarmes

Community Group 2 includes the towns of:

  • Gonaive
  • Ennery
  • Plaisance
  • Saint-Michel-de-l’Attalaye
  • Port-au-Prince
  1. Consider the transmission method and suggest a source of contamination. Be ready to support your hypothesis.
  2. a) What do you think may be a source of the outbreak?


  1. b) Do you have recommendations for testing to find out if your hypothesis is correct?



  1. c) Do you have any questions for citizens or Haitian health workers whose answers would provide you with the information needed to test your hypothesis?



Submit your recommendations, requests for testing, or questions.


Part IV: The Public Health Alert
A public health alert is an announcement that details important health information that the public should know. It defines and updates health conditions regarding communicable disease outbreaks, emerging infectious diseases, immunization updates, and other important information.

Write a public health alert for the cholera outbreak you just investigated and present it to your class. Your teacher may choose other requirements to include.

A public health alert for a disease outbreak includes:

  • What is causing the disease?
  • What are the disease symptoms? progression? fatality rate?
  • How is the disease transmitted?
  • What is the treatment for the disease?
  • What is the target population? Who gets the disease more often?
  • How can the disease be avoided?
  • Where is the outbreak occurring?