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Malaria Facts

Malaria in the United States

  • Malaria was eliminated from the United States in the early 1950’s.
  • Approximately 1,700 cases of malaria are reported every year in the United States, almost all in recent travelers. Reported malaria cases reached a 40-year high of 1,925 in 2011.
  • First- and second-generation immigrants from malaria-endemic countries returning to their “home” countries to visit friends and relatives tend not to use appropriate malaria prevention measures and thus are more likely to become infected with malaria.
  • Between 1957 and 2015, in the United States, 63 outbreaks of locally transmitted mosquito-borne malaria have occurred; in such outbreaks, local mosquitoes become infected by biting persons carrying malaria parasites (acquired in endemic areas) and then transmit malaria to local residents.
  • Of the species of Anopheles mosquitoes found in the United States, the three species that were responsible for malaria transmission prior to elimination (Anopheles quadrimaculatus in the east, An. freeborni in the west, and An. pseudopunctipennis along the U.S./Mexico border) are still prevalent; thus there is a constant risk that malaria could be reintroduced in the United States.
  • During 1963-2015, 97 cases of transfusion-transmitted malaria were reported in the United States; approximately two thirds of these cases could have been prevented if the implicated donors had been deferred according to established guidelines.

Malaria Worldwide

  • 3.2 billion people live in areas at risk of malaria transmission in 106 countries and territories.
  • The World Health Organization estimates that in 2016 malaria caused 216 million clinical episodes, and 445,000 deaths.

Biology, Pathology, Epidemiology

  • Among the malaria species that infect humans, P. vivax and P. ovale can develop dormant liver stages that can reactivate after symptomless intervals of up to 2 (P. vivax) to 4 years (P. ovale).
  • Pregnant women have increased susceptibility to P. falciparum malaria; in malaria-endemic countries, P. falciparum contributes to 8-14% of low birth weight, which in turn decreases the chance of a baby’s survival.
  • An experienced laboratory technician or pathologist can distinguish between P. falciparum, P. vivax, P. malariae, and P. ovale based on the appearance of the parasites and infected blood cells. Under the microscope, P. knowlesi can resemble either P. falciparum or P. malariae. Increasingly reference diagnostic tools like PCR are employed to confirm malaria infection and to determine definitively which species are involved.

Other Facts

  • Five times, the Nobel Prize in Physiology or Medicine has been awarded for work associated with malaria: to Sir Ronald Ross (1902), Charles Louis Alphonse Laveran (1907), Julius Wagner-Jauregg (1927), Paul Hermann Müller (1948), and Youyou Tu (2015).
  • Two important currently used antimalarial drugs are derived from plants whose medicinal values had been noted for centuries: artemisinin from the Qinghaosu plant (Artemisia annua, China, 4th century) and quinine from the cinchona tree (Cinchona spp., South America, 17th century).