4 Treatment and Prevention

Module 4

Introduction to Treatment and Prevention

Have students read the introduction to the module. With polio as an example, students are introduced to treatment and prevention of viral diseases. Polio is an excellent example of a contagious disease that has been greatly reduced worldwide as a result of vaccination programs. Students consider the reasons why polio could be eradicated worldwide but how certain barriers prevent this.

Background on Polio

Imagine a summer without swimming, movies, pickup basketball, or just hanging out with friends. This was a summer experienced by many kids in 1952 when parents felt the safest place for their children was inside the house away from other people. These parents were terrified by the threat of poliomyelitis, an infectious viral disease that was sweeping across the country.

Polio primarily affects children under the age of 5, however adults are susceptible. The most famous case adult case of polio was President Franklin D. Roosevelt who was infected and paralyzed at the age of 39.

Although most infected individuals are asymptomatic (show no symptoms) or experience mild, flu-like symptoms, infection with the poliovirus can result in permanent paralysis or death. The 1952 polio epidemic was the worst outbreak of the disease in the history of the United States. 58,000 cases were reported that year, leaving 3,145 dead and 21,269 paralyzed.

Transmission

Poliovirus is very contagious, with an R₀ of 7 (see Module 3, “Viruses Go Viral”, for an explanation of R₀, a measure of contagiousness), making it far more contagious than Ebola virus (R₀ = 2) but not nearly as contagious as measles (R₀ = 18).

Spread by direct contact, poliovirus reproduces in the throat and intestines. Spread occurs when a person comes in contact with feces of an infected individual or, less frequently, with airborne droplets released in a sneeze or cough.

Water or food contaminated with viral laden feces can also transmit the disease. An infected person, even if asymptomatic, can shed virus for 2 weeks after infection. That is, even a person with no symptoms can still infect another.

Treatment

No cure exists for polio but it can be prevented with a vaccine. In 1954 a massive polio vaccine trial was initiated and 1.3 million children were vaccinated. The vaccine was so effective in this trial that it was made widely available to all children. By 1994 polio was considered eliminated (meaning no longer present in a specific geographical area) in the Americas. A three-year old boy from Peru was considered the last known case (Figure 1).

Figure 1. Luis Fermin Tenorio, last registered case of polio in the Americas

Courtesy of the Pan American Health Organization and World Health Organization

The Case for Vaccination

Because the poliovirus only infects humans and has no animal reservoir, the disease could be eradicated (meaning no longer found worldwide) by vaccinating 80% of the world’s population.

African countries are very close to eliminating polio. However, for economic, social, and political reasons, children living in at least two countries, Pakistan and Afghanistan, are still contracting polio.

Figure 2 shows the change in occurrences of polio from 1988 to 2014 as a result of vaccination programs around the world. In 1980 the World Health Organization announced that smallpox global immunization had eradicated smallpox, the only infectious disease ever completely removed as a threat to worldwide health.

Figure 2. Change in countries with endemic (present in a region) polio between 1988 and 2014

Courtesy of the Journal of the Pakistan Medical Association

Looking Ahead

In this module you will explore approaches to treatment and prevention of infectious diseases caused by viruses.

Although treatment of viral diseases is very limited, public health measures, personal health habits, and vaccination programs can achieve significant reduction of the incidences of these diseases.

You will learn about how your body’s defense system, the immune response, fights off viral infections. You will also learn how vaccines work to initiate and enhance this immune response.

Additional Resources for Module 4 Reading 1

Good neighbours ease fears in Pakistan polio fight, Medical Xpress

This article describes the challenges in vaccinating Pakistan’s children and how these barriers are being overcome.

These two infographics pictorially illustrate the timeline for eradicating polio in general and specifically in Nigeria. Click the thumbnails to view.

Polio: From Iron Lung to Eradication.

Source: Sofia Pasteur

On the Road to a Polio-Free Nigeria.

Source: Rotary International