Epidemiology
There were an estimated 263 million malaria cases worldwide in 2023 in 85 endemic countries (an incidence of 60.4 cases per 1000 population at risk), an increase of 11 million cases compared with 2022, resulting in an estimated 597,000 deaths (a mortality rate of 13.7 per 100,000). Approximately 94% of all malaria cases and 95% of deaths occurred in the African region, and the majority of deaths were due to Plasmodium falciparum infection. Nigeria, the Democratic Republic of the Congo, Uganda, Ethiopia, and Mozambique are the five countries with the most cases.[7]
Approximately 1500-2000 cases are reported each year in the US, almost all in travellers. Transfusion-related transmission and local transmission via mosquitoes have been reported, although this is rare. There were 1823 cases reported in the US in 2018 - including one cryptic case (i.e., exposure cannot be explained despite investigation) and one case acquired through a bone marrow transplant - 15.6% fewer cases compared with 2017. A total of 85% of infections were imported cases that originated in Africa (69.9% of cases from Africa were from West Africa). Visiting friends and relatives was the most common reason for travel. Among the cases with a species determination, P falciparum accounted for 69.8% of cases, with 9.5% of cases due to P vivax, 5.2% due to P ovale, and 2.6% due toP malariae. An imported case of P knowlesi was reported for the first time since 2008.[8] A small number of locally acquired cases of P vivax malaria were reported in Florida and Texas in 2023. These are the first locally acquired cases reported in the US since 2003. Imported cases in three US southern border jurisdictions increased in 2023.[9]
Locally acquired malaria cases in the US (2023)
After 20 years without any recorded locally acquired cases of malaria in the US, 10 autochthonous cases were identified in 2023.[10]
A small number of locally acquired cases of P vivax malaria were reported in Florida and Texas in 2023.[11] These are the first locally acquired cases reported in the US since 2003. There have been no cases of local transmission in Florida or Texas since mid-July 2023.[12]
A locally acquired case of P falciparum malaria was reported in Maryland in August 2023, unrelated to the cases of P vivax malaria reported in Florida and Texas.[12]
A locally acquired case of P vivax malaria was reported in Arkansas in September 2023.[10]
Malaria is not currently transmitted in the UK, but travel-associated cases can occur in those returning from endemic areas. In 2023, approximately 2000 provisional imported malaria cases were reported in the UK (mainly caused by P falciparum). In 2024, approximately 750 provisional imported malaria cases were reported in the UK between January and June.[13]
The World Health Organization aims to reduce global malaria incidence and mortality rates by 90% by 2030.[14] A total of 45 countries and territories have been certified as malaria-free (no indigenous transmission in the previous 3 consecutive years) as of 20 October 2024.[15]
Pregnant women and children aged under 5 years remain the most susceptible to disease.[16] The overall prevalence of malaria in pregnant women living in endemic countries has been estimated to be 18.95%; however, this varied by geographical location. Prevalence was higher during antenatal visits (20.09%) compared with delivery (17.32%).[17]
Almost all cases of malaria in non-endemic areas are imported by people travelling from endemic areas, either as tourists or after visiting friends or relatives. Each year, 25 million to 30 million people from the US and Europe travel to the tropics, of whom approximately 10,000-30,000 acquire malaria.[18]
Occasionally, individuals living near airports contract malaria, either via a local mosquito that has been infected through a blood meal from an infected traveller, or via an infected mosquito from an aeroplane. Rarely, malaria may be acquired via infected blood products, with 93 cases reported in the US from 1963 to 1999.[19] Occasionally, malaria can emerge in supposedly non-endemic regions (e.g., a focal outbreak was reported in Bahia State in Brazil in January 2018).[20]
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