Malaria

malaria, serious relapsing infection in humans, characterized by periodic attacks of chills and fever, anemia, splenomegaly (enlargement of the spleen), and often fatal complications. It is caused by one-celled parasites of the genus Plasmodium that are transmitted to humans by the bite of Anopheles mosquitoes. Malaria can occur in temperate regions, but it is most common in the tropics and subtropics. In many parts of sub-Saharan Africa, entire populations are infected more or less constantly. Malaria is also common in Central America, the northern half of South America, and in South and Southeast Asia. The disease also occurs in countries bordering on the Mediterranean, in the Middle East, and in East Asia. In Europe, North America, and the developed countries of East Asia, malaria is still encountered in travelers arriving or returning from affected tropical zones.

In the early 21st century the incidence of malaria, and the number of deaths caused by the disease, appeared to be declining. For example, the World Health Organization (WHO) estimated that in 2000 there were 233 million cases of malaria worldwide, which resulted in roughly 985,000 deaths, mostly of young children in Africa. In 2010 there were an estimated 216 million cases and 655,000 deaths. By 2018, cases had increased to 228 million worldwide, though deaths had continued to decline, numbering about 405,000 that year.

In 2021 China became the 40th country to be officially declared free of malaria by WHO—by far the most populous country worldwide to have been granted the designation. China had not experienced any indigenous cases for three years in a row, the qualification required to achieve WHO’s malaria-free certification.