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Malaria is among the leading infectious causes of morbidity and mortality in children worldwide. Each year, there are 300 to 500 million clinical cases, causing between 1.5 and 2.7 million deaths, most in sub-Saharan African children under the age of 5 years. Increasing drug resistance, climatic changes, population shifts, economic changes, abandonment of malaria control programs, and insecticide resistance all contributed to a resurgence of malaria in the developing world from the 1970s to the 2000s. Recent World Health Organization, governmental, and nonprofit foundation support for effective preventative measures—such as insecticide-treated bednets, indoor residual spraying, and the implementation of artemisinin combination therapy as first-line treatment for malaria in many sub-Saharan African countries—appears to have significantly reduced malaria incidence and deaths in some countries.1

More than 40% of the world’s population, or 2.5 billion people, are at risk for malaria in 90 countries in Africa, Asia, South and Central America, and Oceania (Fig. 352-1). For many years, it appeared that malaria in humans was caused by four species of Plasmodium: P falciparum, P vivax, P ovale, and P malariae. There is now evidence that P knowlesi, a Plasmodium species that usually infects monkeys, has crossed over to cause malaria in humans in Southeast Asia, notably in Malaysia4; it is now considered a fifth human malaria species. Plasmodium falciparum is found mainly in tropical areas, where warm weather ensures the relatively constant presence of the Anopheles vector. Plasmodium vivax has the widest geographic distribution of the four species and is found in both tropical and temperate areas. Plasmodium ovale is found primarily in sub-Saharan West Africa, where it appears to have almost completely replaced Plasmodium vivax. Plasmodium malariae can be seen in both tropical and temperate zones but is the least common of the malaria species.

Figure 352-1.

Worldwide distribution of malaria.

(Courtesy CDC.)

Diagnostic and treatment approaches differ significantly in malaria endemic countries as compared to countries like the United States, where almost all malaria is imported. In the United States, all of the approximately 1500 cases of malaria that were reported to the Centers for Disease Control and Prevention (CDC) in 2005 occurred in travelers to or immigrants from malaria-endemic countries, with the exception of two cases of congenital malaria, in which the mothers were immigrants from malaria-endemic countries.2 Rare cases of local transmission have been reported in the United States.3

Malaria can be a life-threatening illness. Delay in seeking treatment, misdiagnosis, or both are often seen in individuals who die from malaria in the United States.2 Any febrile child who has been in a malaria-endemic area in the preceding year should be assessed for this illness.

Organisms and Life Cycle

Plasmodium species can infect many different animals but most are host-specific. P falciparum...

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