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About This Module

Topics: Human health, epidemiology, pathogens (bacteria), modes of transmission, emerging and re-emerging disease

Grade levels: 9-12


Students are assigned to investigate a deadly outbreak occurring in Haiti. After reviewing the preliminary information, they know they 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 they may be able to stop the outbreak and prevent more disease!

Learning Objectives

To better understand the ways infectious disease can be transmitted, students should be able to:

  • Compare and contrast different disease transmission methods.
  • Identify ways to avoid infection by pathogens that use direct and indirect transmission methods.
  • Explain how knowing the mode of transmission impacts epidemiology processes and the prevention and control of disease.
  • Analyze epicurves to identify possible causes of the outbreak.
  • Apply knowledge of epidemiological methods and disease transmission to solving a disease outbreak.

Next Generation Science Standards

Standards Aligned to PBL Modules

Introduction to Teacher Notes

 The notes in this teacher version provide the information that you will need to easily implement the activity.  Read the detailed notes in this section carefully for implementation ideas and tips before starting the module with your students.

Case-based learning requires some oversight by the facilitator. The students are, for the most part, working independently, but are guided to learn the content by questions and tasks in the module. In this interrupted case study module, students work on tasks and at key points in their work, you provide them with additional information that they use to solve the problem. The additional information challenges them to reconsider their responses, prompts critical thinking, or adds to the next task.

The teacher notes will guide you through the module. You will know when to distribute the additional information based on student progress. Suggestions for discussions and presentations are included throughout the notes. Teacher notes are listed before each section of the activity. Student text for each section follows for ease of implementation; you don’t have to access both a teacher and a student copy of the activity.

It is important in this kind of activity to have materials copied and ready for student use as teams of students work through the case at varying paces. The Teacher Pages of the scenario include instructions for implementing the case, such as the timing of distributing the additional materials and answers to questions asked in the scenario.

The epidemiological study of a disease outbreak involves a unique application of the scientific method. In this interrupted case study, students will use critical thinking and problem-solving skills to identify the pathogen, analyze epidemic histograms (epi curves), hypothesize the source of the outbreak, identify the transmission method, and recommend containment measures. Some components of the process are presented in the scenario.

Implementation—Several key points

  • Divide the class into student teams of 3-4, depending on your class size and abilities.
  • Introduce the activity by telling your students they will be taking on the roles of epidemiologists from the National Institutes of Health (NIH).
  • Let students know that if instructions tell them to “Report _____”, it means they are to report to you. You will, in some cases, provide them with additional information for working through the scenario tasks or ask them questions about their work.
  • Make sure your students know that at various times, you will be picking a group to deliver a preliminary public health statement and that all their work will be included in their assessment. (Part IV: The Public Health Alert includes a description of what should be included in the public health announcement.) Have the entire chosen team come to the front of the class to report and answer questions. This process should help to keep the groups working as they will not know who you will pick next.
  • You may want to assemble group folders that include all materials for the module. The scenario will be the first piece the students receive. You will distribute other materials including graphs, data tables, news alerts, and maps at appropriate times. Task instructions also contain questions that will guide students through the investigation.
  • You may want to have the groups keep their folders in class during module work. You will know that all student work is done in class and will be able to check group work, at least briefly, at the end of each class.
Scenario (with possible answers)

As an epidemiologist with the National Institutes 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 and 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
Teacher Notes

In Part I, students review the case definition and compare the symptoms of the outbreak disease with the differential diagnoses provided by the fictional Haitian healthcare workers in the field.

If you have groups with very differing ability levels and student teams are working at greatly different paces, then have them submit their reports in writing directly to you when they finish a task. Tasks do not need lengthy reports. You can quickly review their progress and provide feedback to each group.

If your students do not have access to the internet in class, you can print out a classroom set of information on the differential diagnoses from the NIH website listed.  One or two copies for each group will be enough, depending on the size of your student groups, as students within each group will collaborate on the task of eliminating diseases and choosing an initial diagnosis.

If students report an incorrect initial diagnosis, accept it. You will be distributing lab results in Part III: Mapping the Outbreak.

Students also submit their reasons for eliminating a differential diagnosis. Check their work to see if their answers are reasonable as they critically think through this task. Their responses can be part of your assessment rubric. A table, Reasoning for Differential Diagnosis Elimination, is included in the teacher’s materials for your convenience.

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
Teacher Notes

As soon as the students submit their initial diagnosis, distribute:

  • Data Table: Haiti Outbreak Day 1-14
  • Epi-curve: Haiti Outbreak Day 1-14

Allow students some time to analyze the first set of data and answer the questions in this section. Then, tell the students they have just received an update and distribute:

  • Data Table: Haiti Outbreak Day 15-29
  • Epi-curve: Haiti Outbreak Day 15-29
  • Data Table: Haiti Outbreak Day 30-44
  • Epi-curve: Haiti Outbreak Day 30-44

Time the distribution of the additional data group-by-group. If you “miss” the update for one of the teams, the students will see the update announcement in task number 2. It doesn’t matter if the students are not quite finished with the first set of data when you distribute the new data. Distributing the next sets will keep them moving and add to the “urgency” of solving the outbreak.

Students will be submitting hypotheses for possible modes of disease transmission. At this point, they will be considering all possible transmission methods. They will revise the hypotheses when they work through the Mapping the Outbreak tasks and receive more information.

(This is a good time to review the difference between a hypothesis and a prediction, if necessary.)

1. 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. a) Where did the outbreak start? Mirebalais
  2. b) How long did it take to spread from Mirebalais to the next location? about a week
  3. c) Where did the disease spread next? Community 1
  4. d) How long did it take to spread to that location? about 2 days
  5. e) Where did the disease spread next? Community 2
  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?

In Mirebalais and Community 1, the number of cases increased and then decreased.
In Community 2, the number of cases increased slightly and then somewhat leveled off.

Hypotheses for the cause of disease spread to each location and method of transmission will vary.

  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?

Answers will vary. Possible answer:

The number of cases in Mirebalais increased slightly from the levels that were present at Day 14.  If the disease is transmitted from person-to-person, more people may have been infected from other communities since the other locations have so many more infected people. If the disease is transmitted through contaminated water, more people may have been infected by drinking the water.

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

The number of cases in Community 1increased slightly after Day 14, but never gets to the high numbers that occurred during the first week. They remain somewhat steady after that.

The decrease could be that so many people are infected that there are fewer people left to get sick. Also, it could be spread by something other than person-to-person or by contaminated water.

The number of cases in Community 3 increased dramatically in Days 15-29 and Days 30-44 and remain at much higher levels than the other two locations.

Whatever is transmitting the disease has to be affecting a lot more people in Community 3.

Students will not be able to get much more specific than this at this point. They may ask about the population totals for these communities.

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

Answers will vary according to their first hypothesis. Students may ask about populations for the different outbreak locations in their critical thinking of explanations for increases or decreases of case numbers. A table, Populations at Key Haiti Outbreak Locations, is included in Teacher Materials.

Part III:  Mapping the Outbreak
Teacher Notes

Distribute the maps of Haiti included in the module. The maps will help students track the cases and critically think about a possible source of the outbreak.

After they have worked for a short time, tell the students they have now received the lab results on specimens from infected people. Distribute the test results. Ask for updates on their investigations and if they have a short public health announcement they want to submit at this time. They may want to work a little longer on mapping the outbreak.

Next, distribute the alert concerning the Nepalese aid workers’ camp near Mirebalais. (The alert is a separate page in the Teacher materials and listed two/page to save paper.)

Remind the students of the urgency of identifying the source of an outbreak in order to more quickly stop or slow the spread of the illness. Tell them you will shortly be asking for their final decisions and recommendations to control this outbreak.

In this task, students are asked to refine their hypotheses, suggest ways to test their hypothesis, and list any additional information that would be needed to better identify the source.

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.


  1. a) What do you think may be a source of the outbreak?
    Answers will vary, but they should be focused on the U.N. mission camp as a possible source.
  1. b) Do you have recommendations for testing to find out if your hypothesis is correct?

Students should suggest testing at the U.N. camp.

  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.

Answers will vary, but they should be suggesting specific tests for cholera in the U.N. camp. Students could also suggest finding out if any cholera cases were reported in Nepal before the Nepalese volunteers came to Haiti.



The alert concerning the U.N. camp:

The following information was just received from epidemiology field investigators:



The village of Meille (nearby Mirebalais) hosted a United Nations Stabilization Mission camp for international aid workers coming to Haiti to help in recovery efforts after the earthquake. Aid workers and soldiers from Nepal arrived there prior to the first cases of the outbreak disease.

   New reports from field epidemiologists sent to investigate conditions along the Artibonite River have observed questionable sanitary practices, including a pipe discharging sewage from the camp into the river.

Villagers all along the Artibonite River use the water for cooking, drinking, and bathing since the water supply system, damaged from the earthquake, is still being repaired.


Part IV: The Public Health Alert
Teacher Notes

In this section, students write a public health report for the cholera outbreak they investigated. You may want them to submit the report to you for assessment before they report to the class since each group will be able to hear a previous team’s work.

A class debrief is a valuable part of the activity and should be part of the assessment. Depending on the time available, you may want to allow the students to present their work in different formats, such as PowerPoint presentations. Discussion could include details concerning the epidemiological processes they used throughout the activity. Reinforce the concept that National Institutes of Health (NIH) epidemiologists as well as epidemiologists from the Centers of Disease Control and Prevention (CDC) and the World Health Organization (WHO) travel throughout the world to investigate the causes, transmission, prevention, and control of disease outbreaks and epidemics. (Career information can be found in the Pandem Disease Center’s Healthcare Career Directory and Spotlight on Careers.)

After students complete the activity, tell them it is based on actual data from the 2010 cholera outbreak in Haiti which continues today.

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?
  • How can the disease outbreak be contained?
  • Where is the outbreak occurring?