HIV and malaria infections often coexist in patients in many parts of the world due to geographic overlap of these two diseases. This is particularly true in sub-Saharan Africa, where an estimated 40 million people are living with HIV and more than 350 million episodes of malaria occur yearly . There is also evidence of a negative interaction between these two infections. HIV increases the risk of malaria infection and the development of clinical malaria. Conversely, malaria increases HIV replication.
The significant interactions between HIV and malaria infections, including during pregnancy, will be reviewed here. Additional information regarding malaria in the HIV uninfected host is discussed separately. (See "Clinical manifestations of malaria" and "Treatment of uncomplicated falciparum malaria" and "Treatment of severe falciparum malaria".)
There are five malarial species that infect humans. Presently, most data on HIV interaction with malaria are derived from P. falciparum endemic regions of sub-Saharan Africa. However, as HIV spreads to areas endemic for P. vivax, similar important interactions may be identified.
Immunity to malaria — Immunity to malaria is characterized by an age-related reduction in parasite burden, clinical symptoms, and prevalence of severe disease in individuals residing in an endemic area . P. falciparum infection and the burden of parasitemia are often less severe in older adults than in children. Children are at increased risk since they have not yet acquired natural immunity; pregnant women transiently lose some of their acquired immunity due to the relative immunosuppression of pregnancy. The degree of immunity is also related to transmission intensity, which varies geographically. HIV-related immunosuppression diminishes this acquired immunity. (See 'Impact of HIV on malaria' below.)
Clinical versus asymptomatic malaria — As discussed above, individuals living in endemic areas may develop partial immunity to disease following repeated infections. These "immune" individuals are not immune to infection per se. Following a bite by an infected mosquito, they will still develop parasitemia, but the severity of clinical symptoms is typically limited. This can affect estimates of clinical infection since patients who live in endemic areas are much less symptomatic and often have no symptoms. (See "Clinical manifestations of malaria".)