- Reading 1 Module Introduction
- Reading 2 Patient Zero
- Reading 3 John Snow
- Activity 1 Causative Agent
- Activity 1 Discussion
- Activity 2 Tracking the Spread
- Activity 2 Resources
Ebola and Measles on the Move: Tracking the Spread
The purpose of the activity is to have students explore the role of human behavior in the spread of Ebola and measles.
While human behavior is a factor in diseases that are the result of contaminated food and water — humans fail to keep excrement out of their water supplies (cholera) and humans fail to practice sanitary procedures during food preparation (Salmonella infections) — these diseases can be stopped by regulating city and town water supplies and food preparation by companies.
Changing human habits requires education of the population about dangers of certain practices, some of which are steeped in personal beliefs, traditions, and long-standing habits.
While the biology and ecology of infectious agents plays an important role in determining their spread, the emphasis in this activity is primarily on human behavior. The biology and ecology of viruses as determinants of infectivity is explored in greater depth in the Module 3, Viruses Go "Viral".
In this activity students identify factors that influence the spread of Ebola and measles and suggest ways that could prevent or halt outbreaks and epidemics based on their findings. You may want students to then design an intervention or program to educate individuals about the dangers of a practice and that could help individuals change or eliminate that practice.
One copy of the Factors Chart (downloadable below) for each student or for each team if activity is done collaboratively.
On the digital version of the chart below, click "show factors" to see the factors influencing the spread of each disease highlighted in blue.
|Animal reservoir||No animal reservoir|
|Transmission - direct contact with body fluids from infected individuals||Transmission - aerosol through inhalation of droplets from lungs of infected individuals|
|Not very contagious||Highly contagious|
|High fatality rate (50–90%)||Moderate fatality rate (1–30%)|
|Recently developed vaccine; highly effective but not widely available||Effective vaccine; widely available|
|Likely immunity after infection or vaccination||Definite immunity after infection or vaccination|
|Burial customs in a country have relatives touch the body of the deceased person||Burial customs vary|
|Global travel is highly common across many nations||Global travel is highly common across many nations|
|Access to healthcare limited in many affected countries||Access to healthcare varies in affected countries|
|Access to clean water limited in many affected countries||Access to clean water varies in affected countries|
|Wild animals used as food source in many affected countries||Wild animals may be used as food in affected countries|
|Mutations in the viral genome occur as the virus moves from person to person||Strains of the measles virus,can be identified by antibody assays of surface proteins|
Notes on the above chart:
- The existence of an animal reservoir makes it very difficult to eliminate an infectious disease. Measles with no animal reservoir could be eliminated if .90% of individuals were vaccinated. Eliminating the reservoir is probably not feasible
- Direct or close contact is involved in the spread of disease. If patients were isolated the spread could be limited or halted
- The infectivity of the virus is a factor. This factor will be discussed in greater depth in the Viruses Go “Viral” module
- It could be argued that the greater the fatality rate the lower the spread because patients die. However, this is probably not a major factor in Ebola or measles.
- Burial rituals are a definite factor in the spread of Ebola whereas are not a factor in measles. Altering burial rituals or have no contact with the body during burial would prevent infections.
- Global travel was definitely a factor in the spread of both Ebola and measles. Checking travelers for illness or stopping travel from countries with the disease perhaps could confine the spread.
- Access to healthcare meant many patients with Ebola remained in homes and were attended by families with no protective gear or practices so they became infected. At first signs of illness, patients could be admitted to a facility dedicated to Ebola patients. Such action could prevent the spread to family and caretakers
- The consumption or association with wild animals carrying Ebola was likely a factor in initiating the epidemic (see Patient Zero) but is probably not involved in the spread of the disease. Since measles has no animal reservoir it is definitely not involved.
- Changes in the virus have no known role to date but do allow epidemiologists to track the path of the epidemic as it spreads.
Distribute Factors Chart to students. Inform them that, based on their understandings so far about Ebola and measles, they will identify factors involved in the spread of these infectious agents and factors they may make its elimination possible or difficult. You may want them to look at the Ebola and measles information found in the Epidemics timeline.
- Have students identify the factors they deem important in the spread and justify their decisions about why they think each factor is important. They should also consider how these factors could be altered or changed to prevent or halt an outbreak or epidemic. Students should be prepared to share their decisions and justifications.
- Have students share their decisions and reasoning in a whole class discussion and discuss ways that these factors might be eliminated or altered.
- You may want to facilitate a discussion regarding the challenges of changing certain behaviors. For example:
- Changing habits or traditions based in deeply held personal or religious beliefs
- Economic factors in poor countries
- Ethical concerns regarding enforced isolation of infected individuals or in barring travel from certain countries or in requiring vaccinations for every child.
- On January 14th, 2016, the World Health Organization announced the end of the Ebola epidemic in Liberia. Both Sierra Leone and Guinea, the two other countries that were devastated by the recent Ebola epidemic – had been pronounced Ebola-free earlier. These epidemics claimed 11,000 lives in these West African countries before the epidemic was halted. You may want to discuss this with your class and elicit their thinking on how the epidemic was halted.
An article from the WHO discusses how the epidemic was halted by "Detecting and breaking every chain of transmission." It also raises a cautionary warning that because the Ebola virus remains in the semen and eye fluids in some survivors, the WHO and other health and government organizations must remain vigilant for more outbreaks and be prepared to stop them before they spread.
In the reading about patient zero, you learned that Ebola spread initially from the toddler to members of his immediate family and caretakers, then on to individuals who attended the funeral. From there the disease spread exponentially across west Africa, moving victim to new victim through direct contact with virus-laden bodily fluids.
Measles spread from patient zero to other individuals through the inhalation of virus-laden droplets cough up from the victim’s infected lungs. The spread of measles does not require direct contact but can spread easily to anyone in close vicinity to the infected individual.
Cholera is different in that it does not spread from person to person but rather from a definable source – contaminated water. Remove the source – in the case of the cholera epidemic of 1854, the offending pump – the epidemic is halted. In the case of waterborne diseases, outbreaks and epidemics can be prevented by providing clean water, a seemingly simple solution but not so easy in many countries.
Halting or preventing epidemics spread through direct or close contact is not easy either. In many cases it requires altering human behavior, no simple task. In the following activity you will identify factors that facilitate the spread of Ebola and measles and based on your findings, suggest ways the spread of each could be prevented.
You should review the information on the timeline related to Ebola and measles before you begin.