Epidemiology

Malaria is primarily a disease of humid, hot countries below an altitude of 2000 metres above sea level. It is these environmental features that favour the prolific breeding of the mosquito vector, Anopheles.

Endemic and epidemic malaria is found in all countries between the latitudes 30 degrees south and 40 degrees north.

• malaria is endemic in India, in parts of Africa and South and Central America

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). (1)

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. (1). Malaria has a mortality rate of <1%.

• out of the five species, P. falciparum and P. vivax are the most important
  • P. falciparum is the most deadly form, and it predominates in Africa (1)
  • P. vivax has a wider distribution than P. falciparum because it is able to develop in the Anopheles mosquito vector at lower temperatures, and to survive at higher altitudes and in cooler climates
    • although P. vivax can occur throughout Africa, the risk of P. vivax infection is consider ably reduced in the region by the high frequency of the Duff y negativity trait among many African populations; in individuals without the Duff y antigen, red blood cells are resistant to infection with P. vivax
  • in many areas outside Africa, infections due to P. vivax are more common than those due to P. falciparum (1)

In the UK, the most common type of malaria is the potentially fatal falciparum malaria, which is usually acquired in West Africa. In 2023, 2,106 cases of imported malaria were reported in the UK (1,977 in England, 90 in Scotland, 30 in Wales and 9 in Northern Ireland). This is 26% higher than numbers reported in 2022 (1,555 cases) and 3% higher than the mean number of 1,504 cases reported annually between 2014 and 2023.

This is the highest total number of cases seen in the UK since 2001 where the total case number was above 2,000. A total of 6 deaths were reported in 2023, which is the same as the annual average of deaths between 2014 and 2023. (2)

Malaria epidemics can occur when climate and other conditions suddenly favour transmission in areas where people have little or no immunity to malaria. They can also occur when people with low immunity move into areas with intense malaria transmission, for instance to find work, or as refugees

Reference:

1. World Health Organization. World malaria report 2024. Dec 2024 [internet publication].

2. UK Health Security Agency. Malaria imported into the UK: 2023. Updated 3 December 2024 [online]