|About This Module|
Topics: Human health, epidemiology, pathogens (viruses), modes of transmission, re-emerging disease
Grade levels: 9-12
Students investigate a fictional outbreak of Ruzizi Virus Fever in Mexico. They work to identify the disease transmission method in an effort to control and contain what looks to be a re-emerging disease outbreak.
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.
- Describe how viruses cause disease.
- Explain how knowing the mode of transmission impacts epidemiology processes and the prevention and control of disease.
- Apply knowledge of epidemiological methods and disease transmission to solving a disease outbreak.
|Scenario (with possible answers)|
“Another viral outbreak alert? You’re kidding. How many does this make in the last three months?” You are not all that surprised. In your work as an epidemiologist at the National Institutes of Health you are used to monitoring outbreaks of infectious diseases both in the U.S. and around the world, but it does seem like they are coming closer together.
Your colleague and friend, Kelly, delivers the news. “We’re being assigned to investigate what might be happening with this virus. It’s not a novel virus, but has, all of a sudden, popped up in a completely different location than where it occurred before.”
She hands you information from the director on the Ruzizi Virus Fever (RVF), some maps of Mexico, and patient interviews conducted by field epidemiologists and tells you that the director wants an analysis as soon as possible.
“OK”, you say to Kelly, “Let’s go through this info and then we can start to plan our next moves.”
After reading the information, you look at Kelly and know you are both thinking the same thing: Ruzizi Virus Fever is a re-emerging disease that seems likely to be a major infectious disease given its rapid increase in the number of cases. You both know that time is a critical factor in containing
the outbreak, but without known transmission methods or an effective vaccine, there is little hope of preventing or containing the disease quickly.
Investigators in the field have already sent you some patient data and interviews so that your team can identify clues that may lead to the transmission method. Somewhere in the patient interviews there are the clues you need to find in order to identify the transmission method of the Ruzizi virus. You know that identifying the transmission method is key to prevention and containment. You also know that a disease can be transmitted in more than one way; identifying each transmission method is important.
The outbreak seems to be centered in the Mexican state of Chihuahua, which shares a long border with the U.S. states of Texas and New Mexico. Given the proximity to the U.S., health officials at NIH and the Center for Disease Control and Prevention (CDC) are concerned that the virus may spread across the border.
Chihuahua has varied climates and ecosystems, including forests, mountainous regions, canyon systems, and wide river valleys. Several river systems allow for good farming of a number of different crops. Temperatures vary with the environment, but reach over 100o F in some areas.
Review the RVF information and patient interviews for clues to figure out how this disease may be transmitted. Knowing how the disease is transmitted will help identify prevention and control strategies and may possibly allow the outbreak to be controlled quickly. You know you have to find answers quickly and accurately to include in your briefing for your colleagues at the NIH and CDC and for public health officials anxiously awaiting some guidance.
1) What are possible transmission methods for Ruzizi Virus Fever given the information in the description and the patient information and interviews? After reading the patient interviews, make a list of every possible transmission method based on patient information.
The students should list the possible types of transmission methods that may be causing this outbreak. Accept all types of transmission possibilities at this stage.
- direct contact with blood or body fluids
- contact with contaminated objects
- contact with infected animals
- zoonotic–bite of mosquitos (Aedes), rodents, bats
- sexual contact
- person to person
2) Of course, no official decision would be made until scientific evidence from laboratory testing was available. However, you can narrow the transmission methods you listed to the three most likely methods. Give your reasons for eliminating the transmission methods.
Examples of those transmission methods eliminated:
- direct contact with blood or body fluids –No evidence from patient interviews of blood or body fluid contact that would account for this method.
- contact with contaminated objects—Possible but not very likely that all victims would have touched infected objects.
- contact with infected animals—Only one patient (Esteban P.) worked on a ranch where an infected animal may live. This method does not account for the geographic distribution of the cases or the number of cases in the outbreak.
- bite of mosquitos (Aedes), rodents, bats (zoonotic)-possible
- sexual contact—possible
- respiratory—This seems unlikely due to the fewer numbers of cases so far. Respiratory outbreaks usually involve very quick spread of infection and high numbers of cases.
- waterborne—The Rio Conchos River is a major source of water for thousands of people. If the water supply was contaminated, you would expect much larger numbers of cases.
Therefore, the three most likely transmission methods are:
- contact with contaminated objects
- zoonotic—bite of mosquitos, rodents, bats, etc.
- sexual contact
3) How could each of the three most likely transmission method be tested to find out if it could be spreading the disease in Mexico?
- contact with contaminated objects—Objects in victims’ homes and at places of employment could be tested for the RVF virus.
- zoonotic—Prevalent vectors in this environment include mosquitos, rodents, bats, and fleas. Insects, rodents, bats, and other species in areas where infected persons lived or worked could be gathered and tested for the presence of RVF. Patient histories could include questions about insect or animal bites.
- sexual contact—Victims’ contacts should be found and questioned. Administer contact surveys to determine if sexual contacts of patients were infected. One victim’s wife has become ill; more case data should be collected.
4) Which transmission method(s) is your top choice? You may list more than one if the patient interviews suggest more than one method.
zoonotic infection—spread by the bite of infected mosquitos, rodents, bats, fleas, etc.
sexual contact—Fernando’s wife also got sick.
5) Laboratory testing can take weeks depending on the type of test. Public health officials want to begin prevention, control, and containment measures as soon as possible so new cases, illness, and deaths are kept to a minimum. Often, prevention and control measures are instituted before test results are obtained. Based on the transmission methods, what prevention and control strategies will you and your team suggest to public health officials?
Ruzizi is most likely spread through the bite of an infected vector. You can prevent getting Ruzizi Virus Fever by avoiding bites from insects and other animals until the actual vector for Ruzizi is identified; specific prevention and control procedures will then be applied.
To avoid insect bites:
- Wear long-sleeved shirts and long pants.
- Try to stay in places with air-conditioning and use screens in windows and doors if air- conditioning is not available.
- Control insects inside and outside the home.
- Use a mosquito net around your bed if you cannot control insects.
- Use an insect repellant.
5) Why do you think that only the severe form of the virus and disease showing up now?
The Ruzizi virus may have changed so that it causes only the more severe form of the disease.
In this module, students will analyze patient interviews in order to identify the disease transmission method. A few hints are listed here at the end of each interview. If students are “stuck” in their review and are not quite sure of how to go about using the information in the interview and applying it to disease transmission methods, you can use the hints to get them started.
Advise the students to list possible transmission methods indicated by the interview and
to make note of any information they feel may relate to transmission.
1) Juan G.
I don’t know how I got sick. One minute I was fine and then I got a fever and headache. I was not feeling too bad, but still not completely well. My muscles and joint hurt and I just thought it must be the flu.
I wasn’t able to go to work for a week and I never miss work. The headache and fever were too bad and my muscle and joints hurt. I have a physical job, so I wasn’t able to go to work. I live in Delicias and work at one of the factories in Naica making furniture.
Why are people asking questions about the flu? Is this the flu?
Examples of notes:
Juan was going to work and home. He could have gotten the disease at either place or
even along the way.
Are people who were contacts of Juan getting sick? in Delicias or in Naica?
Person-to-person is possible.
2) Maria T.
I was the first to get sick in my family, but eventually we all got it. I live in a very small town on the Rio Conchos near Camargo. We have about 150 people in our town and most of the families have someone who works with the crops. They grow mostly sugarcane and beans near own town, but not far away, the crops are more tomatoes, chili peppers, and fruits. Some people from our town go all the way to Delicias to pick the fruit when the crops here are all picked.
I got sick first with the fever, headache, and muscle aches. I still went to work for a few days because we need the money, but then I got too sick. It lasted for about one week, but now I think I am getting worse. I know a lot more people who are sick now. I also heard that people in Aldama are getting sick, but some are much worse than I am. I heard that they were taken to the hospital. My headache is getting much worse and I hope I don’t have to go to the hospital, too.
Could still be person-to-person. Patient lives in a small town and more people are getting
Most people in Delicias work with crops grown there.
People in Aldama are getting sick as well.
All the people in this patient’s small town live near the Rio Conchos River. Could this be a water-borne illness?
Could this be vector-borne as insects and other vectors often need warm, humid places for breeding?
Delicias (where patient #1 lives) is also on the Rio Conchos River.
3) Pablo R.
I got sick about one week ago and am still feeling pretty bad. I had a fever and a bad headache. Then I started to vomit. I felt like I was getting a little better, but then the doctor said that I should go to the hospital. He said that they wanted to do some tests and watch what happened to me. He said that whatever is making everyone sick could get worse.
The trip from Aldama where I live to Camargo to the hospital was hard because I felt so sick. Now, I’m at the hospital, but still not getting better.
I wasn’t the first one in my town to get sick. There were other people sick but I didn’t think I would get it. I don’t get sick very often.
I work nearby on the farms. My job is to make sure the irrigation system that goes from the river to the crops works. There is usually a lot to do to keep it running and check the workings.
He lives in Aldama (where other people are getting sick) and works with the irrigation
system on a farm. Is this a water-borne illness?
4) Bernardo P.
I live in Delicias, Chihuahua. I work on the farms nearby. It is a good living because there is always work because the crops need to be picked at different times.
I got sick about two weeks ago and I thought I would get better. Now, I am worse and the doctor said I should go to the hospital because he didn’t know what was the matter with me or with the other people who are getting sick.
But, I’m not getting better and I’m worried now that my family will get sick with this, too. So far, they are not sick but people know now not to get around other people who may be sick. At first, we didn’t think too much about it, so we didn’t avoid crowds or anything. Now, I think maybe that’s what we should have done.
Works on a farm and lives in Delicias. The patient worries that his family will get sick
from him and indicates other people thought that the disease was spread person-to-person; he thinks he should have avoided crowds.
If this disease is not spread person-to-person, would it have helped Bernardo P. to not
get around people?
5) Fernando C.
This patient’s wife has confirmed that he became ill about two weeks ago and did not seek medical help until well into the second week. The patient’s illness began as fever and muscle aches with nausea and vomiting, but progressed to severe headache with memory loss and confusion. The patient went into a coma and has died.
The patient’s wife is now beginning to feel nauseous and has a fever.
They lived in Naica and Fernando worked part-time in the gypsum mine there and part-time at the hydroelectric plant off the Rio Conchos. They have six children who are not sick at this point.
Patient lived and worked around the water of the Rio Conchos River.
His wife is now ill. Could this be sexually transmitted?
His six children are not sick, although his wife is ill. Could this be a person-to-person transmission?
6) Gabriella D.
I got sick about a week ago and can’t seem to get better. I have been staying in bed to rest and the fever is not getting any better. I ache all over, but you would expect that if you have a fever. I have some nausea, so this must be the flu, but I have never had the flu that lasted this long.
I heard that a few other people are sick, too, but not that many in my small town. Usually, a lot of people get the flu—it spreads quickly. A neighbor is looking in on me since I live alone and she told me that other people are getting sick now. She has come to see me every day and she isn’t sick, so I’m glad I haven’t made her sick.
My work? I work over in Camargo at a park. A lot of people go to the park because of the lakes and hot waters there. It’s a beautiful place to work.
This patient works at a park with lakes and water features.
7) Esteban P.
This patient is in a critical care unit in a hospital in Camargo. (The Hospital Del Angel has already received 14 patients with severe complications of what is suspected to be RVF.)
Patient history indicates that he was otherwise a healthy 22-year old adult male. He lives in a small village near Camargo and worked at a cattle ranch nearby.
The patient has memory loss and confusion and has had several episodes of seizures. Neurological involvement appears to be progressing and life support efforts continue.
This patient works in an outside environment as well. He lives near Camargo where other people are sick.
Additional Notes: Student presentations should provide their hypotheses for disease transmission methods. They should be able to explain and defend their hypothesis and explain why they eliminated other choices.
Since student groups will be presenting in front of each other, you may want to have them submit their report to you prior to the presentations. You will be able to assess each group more accurately if they haven’t heard another team’s report.
You may want to have student teams present different patient interviews so each team is analyzing and adding to or eliminating transmission methods.
Allow the students to ask questions of other teams, if they have questions. Monitor other teams’ questions for suitability.
Assess student understanding of emerging and re-emerging disease. They should be able to name and discuss current emerging and re-emerging diseases. Examples that have been prominently in the news include Ebola, influenzas, TB, measles, and mumps. Other examples with details are listed in the “Table of Emerging and Re-emerging Diseases” in the support materials for this module.
Additional Questions you may want to ask in class: (Some may have been answered in their presentations.)
1) Bernardo says that maybe he should not have gotten around people. If it wasn’t person to person, will it help to not get around people?
2) What would make you think it was not person-to-person?
Whole families are not getting sick. Victims are mainly people who work outside.
3) What evidence is there that the virus is spread through the water? What evidence leads you to think that it is not water-borne?
The people who are sick live near the river or work near the river. Not everyone who drinks the water is sick.
Information about constructing and implementing rubrics for problem-based learning strategies can be found in Developing Rubrics in the Teacher Professional Development section.
► Invite your county or district public health officer or an epidemiologist from a local university (or both) to talk to your classes about how public health is monitored in your area.
► Have your students complete another problem-based learning module that focuses on an outbreak. The Outbreak! module uses an interrupted case study approach that allows your students to work the outbreak step-by-step, receiving reports and alerts throughout their work.
► Watch the Frontline PBS documentary “Outbreak” which details the 2014-2015 Ebola epidemic in West Africa. The video describes how it may have started, what caused it to spread through several West African countries, and how mishandling of key epidemiological practices resulted in thousands of deaths. It also details the epidemiologic investigative process used in the outbreak.
NOTE: Be sure to watch this video before showing it to your class. At times, this video is difficult to watch. It shows people who have contracted Ebola and present s desperate conditions in medical camps built to deal with Ebola cases. It is an excellent video that highlights the different factors, including social, cultural, political, and economic issues that influence the efforts of dedicated medical professional in trying to stop the epidemic, but it may not be suitable for all classes.
Access the Frontline Outbreak! video at http://www.pbs.org/wgbh/frontline/film/outbreak. You can also access the teacher and student Study Guide from this site.
► For a more personal perspective on disease investigations, have your students watch the NOVA 14:40 minute “Zika: The Untold Story”. This interesting and well-narrated video describes the discovery of the Zida virus in 1947 in Uganda by Alexander Haddock and the subsequent study of the virus by his grandson, Andrew Haddock. The video describes Zika’s recent re-emergence as a dangerous viral infection. Access the video at http://www.pbs.org/video/2365909836/
Additional resources about emerging and re-emerging diseases can be found:
in the Key Resources section in the Pandem Disease Center at http://www.pandemsim.com/pdc/index.php/key-resources/
in the Ruzizi module background materials (Internet Resources for Emerging and Re-emerging Diseases) at http://www.pandemsim.com/pdc/index.php/internet-resources-emerging-and-re-emerging-diseases/