epidemiology

Last edited 05/2022 and last reviewed 02/2023

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 latidudes 30 degrees south and 40 degrees north.

• malaria is endemic in India, in parts of Africa and South and Central America
• in 2013 there were 104 countries and territories in which malaria is presently considered endemic (97 countries and territories with ongoing malaria transmission, and 7 countries in the prevention of reintroduction phase) (1)

Malaria affects more than 200 million people world-wide. It has a mortality rate of <1%.

• according to the WHO estimates, there were 207 million malaria cases and 627,000 malaria deaths worldwide in 2012
• most cases (80%) and deaths (90%) occurred in Africa and most deaths (77%) were in children under 5 years of age (in Africa a child dies every minute from malaria) (1,2)
• 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 UK:

• the most common type of malaria is the potentially fatal falciparum malaria, which is usually acquired in West Africa.
• in 2012 there were 1378 reported cases malaria (a decrease from the 1,677 cases reported in 2011)
• 73%  were due to Plasmodium falciparum acquired in Africa (669/1,378 or 49% from West Arica)
• 271 cases were due to Plasmodium vivax
• with P. ovale and P. malariae accounting for the rest of the cases
• there has been an increase in cases among travellers returning from the Indian-subcontinent (increased by 22 per cent, from 274 cases in 2010 to 334 cases in 2011) (2)
• this increase in cases from the Indian-subcontinent in 2011 is largely due to a doubling of cases of Plasmodium vivax malaria acquired in Pakistan
• in 2011, eight deaths from malaria were reported, six from falciparum malaria acquired in Africa and two from vivax malaria acquired in India (2,3).

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 (WHO). World malaria report 2013
• (2) Public Health England (PHE). Press release 2012. HPA reports 22 per cent increase in malaria cases returning from the Indian sub-continent  
• (3) Health Protection Agency. Health Protection Report. 2012;6:17-27.