Epidemiology is the study of diseases as they occur in living things. It focuses on understanding the transmission, spread, and control of diseases. From an epidemiological perspective, the basics of malaria are well known. Malaria is not spread from person to person like a cold or the flu is. Rather, in the act of feeding, a female Anopheles mosquito transmits disease parasites to a human.

The mosquito is the most dangerous transmitter of disease on Earth. It is responsible for malaria, yellow fever, dengue fever, West Nile virus, and more—serious diseases that together affect hundreds of millions of people around the world each year. Diseases transmitted by mosquitoes, fleas, ticks, or some other living agent are called vectorborne diseases. A vector is an organism that does not cause disease itself. Rather, it spreads infection by transporting disease-causing microbes, such as viruses, bacteria, and certain parasites, from one host to another. Once in the body of a new host, these microbes reproduce.

Malaria occurs in more than 100 countries and territories, almost always in warmer climates. Each year, more than 300 million cases of malaria are reported worldwide. While malaria can strike almost anyone in a population, most of those who die from the disease are children. In fact, more than 1 million children under five years of age are killed by malaria in Africa alone. As the video explains, malaria is viewed by many public health professionals as a primary reason for Africa's continued poverty.

Unfortunately, there is currently no malaria vaccine approved for human use. The malaria parasite is a complex organism with a complicated life cycle. Like other parasites and viruses, it is surrounded by a protective coat of proteins. For a vaccine to be effective, it must stimulate production of antibodies that are an exact molecular match of these coat proteins. Developing a vaccine against the parasite has proven difficult because the malaria parasite's protein coat is constantly changing. While effective antimalarial drugs exist to treat malaria patients, they are too expensive for most Africans. And even though malaria has been eliminated in other places before, including the United States and Brazil, the tactics of destroying mosquito breeding grounds and household spraying of pesticides like DDT are either impractical or too controversial to work in Africa.

But one low-cost, low-tech solution based on a simple understanding of mosquito behavior has been shown to be 90 percent effective in preventing disease transmission: creating a barrier between sleeping humans and mosquitoes that prefer to feed at night. This barrier can be easily established using bed nets. Today's insecticide-treated bed nets last for five years, unlike earlier nets that needed retreatment every few months.

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