Modern approaches to disease control include cooperation among nongovernmental organizations and governments, education, and awareness of culture and values, as well as medicines and vaccines.

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Diarrheal diseases are caused by a variety of bacteria, viruses, and parasites transmitted in water that is contaminated by feces. Thus, diarrheal diseases, which cause 2.5 million deaths per year, are most prevalent in countries with poor sanitation systems. According to the WHO, 88% of diarrheal diseases can be directly attributed to poor sanitation and hygiene. Young children are especially susceptible to diarrheal diseases, and half the victims of diarrheal diseases are children younger than 2 years old.

Reducing or eliminating diarrheal diseases hinges on better conservation of drinking water and management of waste. Improved water supplies can reduce diarrhea cases by 21%, while better sanitation can reduce them by 37.5%. Simply providing access to a latrine reduced incidence of diarrhea by 24% among children under 5 years of age in Lesotho, South Africa.

In remote villages and logging camps in Africa and elsewhere, locals continue to hunt and eat wildlife, including fruit bats, gorillas, and porcupines, that may harbor deadly viruses such as Ebola. Although many people turn to bushmeat and wild game because it is a cheap and readily available source of protein, it also plays a cultural role in some societies; this has led to a rampant national, and sometimes international, trade in bushmeat.

At John F. Kennedy airport in New York, U.S. customs agents frequently confiscate bushmeat that African nationals have brought into the country for friends and relatives. Some of these wild species are endangered or already protected, thanks to local laws and international treaties; but one of the best ways to reduce the probability of zoonotic outbreaks is through public health campaigns that emphasize the dangers of harvesting certain animals. In addition, ensuring food security among rural populations will also go a long way toward reducing reliance on bushmeat.

Most attempts to control malaria, primarily by eradicating mosquitoes, have not been sustainable. Health workers have long recognized that environmental changes can impact mosquito populations and the spread of malaria. Dams and irrigation projects provide breeding grounds for mosquitoes and reducing standing water is critical to limiting their populations. Attacking the disease requires a two-pronged approach, focusing on both the environmental factors that allow mosquitoes and malaria to thrive, and a way to prevent it from being transmitted to humans.

One of the most promising approaches to reducing rates of malaria infection, especially of young children and pregnant women, combines insecticide-treated mosquito nets with indoor spraying. Mosquito nets treated with pyrethroid insecticides, which are natural plant products and biodegradable, are hung over beds to protect people while they sleep (Figure 11.19a). Spraying the interior of houses with one of several insecticides, including pyrethroids, further reduces the rate of malaria infection (Figure 11.19b). As shown in Figure 11.19c, combining indoor spraying with insecticide-treated nets reduced rates of malaria infection by over 50% in areas with a medium risk of transmission and over 30% in high-risk transmission areas.

The research on the effectiveness of insecticide-treated nets is a cooperative project between the London School of Hygiene and Tropical Medicine (LSHTM), a leader in research on tropical diseases for over a century, and the WHO. This project and others developed by LSHTM have received extensive funding by the Bill & Melinda Gates Foundation, a leading donor to malaria research and response. Such cooperation is a crucial part of finding a solution to any complex, large-scale environmental health issue. In the case of malaria in Africa, the results of such cooperation have been significant. As insecticide-treated nets and indoor spraying techniques have been widely applied, the number of malaria cases and deaths from the disease has decreased substantially across sub-Saharan Africa (Figure 11.20).

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Tuberculosis (TB) is a bacterial infection that usually attacks the lungs. Cases of TB occur throughout the world, but it is most prevalent in sub-Saharan Africa and Central, South, and Southeast Asia. Controlling the disease has become a major challenge to public health systems worldwide. People at greatest risk of contracting TB are the elderly, infants, and those with weakened immune systems. The risk of contracting TB increases when individuals are in frequent contact with someone already infected, have poor nutrition, or live in crowded or unsanitary conditions (Figure 11.21). This is part of what we mean when we talk about an individual’s cultural and social environment. Stamping out TB requires changing that environment.

One program receiving one of the widest applications is the directly observed treatment system, or DOTS, of the WHO. The centerpiece of the DOTS therapy is that patients diagnosed with TB take the treatment while being directly observed by trained personnel over the 6 to 8 months generally required for effective treatment. Direct observation ensures that all treatments are administered, thereby maximizing the chance for a successful cure while minimizing the risk of incomplete treatment, which runs the risk of producing antibiotic-resistant bacteria.

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The DOTS system of treating TB combines the advantage of low expense with effectiveness. As a result, estimates by the WHO indicate that DOTS treatment prevented approximately 20 million deaths between 1995 and 2013. However, the DOTS treatment is effective only against strains of TB that are not drug resistant. Treating cases of multi-drug-resistant TB (MDR TB) requires up to 2 years and is much more expensive. Treating rare cases of extensively drug-resistant TB (XDR TB) are even more difficult and costly.

A broad partnership of organizations has been formed to combat these much more difficult forms of TB on a global scale. The partnership involves several governmental and nongovernmental organizations, including (again) the Bill & Melinda Gates Foundation, which has been one of the largest nongovernmental contributors to programs aimed at combating TB. For example, the foundation donated over $112 million in 2011 to support development of better tools for addressing the global TB epidemic, including shorter and simpler treatments, new and improved vaccines, and better diagnostic tools. The foundation works as an advocate for wider access and reduced TB treatment costs around the world.