Almost all cases in the U.S. are acquired during travel to countries where malaria occurs. The malaria parasite is carried by infected humans in their bloodstream. When a mosquito ingests blood from an infected person, the malaria parasite develops into an infective stage within the mosquito and later is injected into another person when that infected mosquito feeds again. Malaria can also be acquired by receiving a blood transfusion from an infected donor, and by the sharing of contaminated syringes. Rarely, the parasite can be passed on to infants born to infected mothers.
Malaria is a disease commonly characterized by fever, chills, headache, and sweating.
The infected person may develop relapses throughout their life. Malaria caused by Plasmodium falciparum , the most serious form of malaria, may progress to organ failure, coma, or even death. The appearance of symptoms is dependent on the species of Plasmodium but can vary from 7 days to 10 months. Malaria is common in most tropical and sub-tropical countries. Travelers to Central and South America, the Caribbean, sub-Saharan Africa, India, Southeast Asia, the Middle East and South Pacific are especially at risk.