Level of risk of exposure to malaria and what affects it
Exposure of individual travellers to malaria is influenced by the number of infectious bites received
Factors affecting the number of infectious bites received are given below:
- Temperature, altitude and season
- optimum conditions for malaria transmission are high humidity and an ambient temperature in the range 20 to 30 degrees C
- Malaria transmission does not usually occur in regions with temperatures below the 16 degrees C isotherm (line on a weather map joining all the places that have the same temperature)
- parasite maturation in the mosquito usually cannot take place at altitudes greater than 2000 metres
- has been reported at altitudes up to 2500 metres in some countries
- seasonal rainfall increases mosquito breeding and in some areas malaria is highly seasonal
- Rural versus urban location
- Malaria incidence is generally higher in rural than in urban areas, especially in Africa where the intensity of transmission is on average about 8 times higher in villages than towns but as Africa becomes increasingly urbanised, the risk of contracting malaria in African or other cities of malaria-endemic areas must not be discounted
- Type of accommodation
- an impregnated bed net should be used unless the accommodation is fitted with functioning air-conditioning and windows and doors which are sufficiently well sealed to prevent mosquito entry
- backpackers staying in cheap accommodation have a higher risk of being bitten compared to tourists staying in air-conditioned hotels
- a traveller should embark on their journey equipped with mosquito protection measures appropriate to their particular circumstances
- Patterns of activity
- being outdoors between dusk and dawn when Anopheles mosquitoes bite increases the risk
- Length of stay
- longer the stay, the higher the risk of contracting malaria
Reference:
- Public Health England. Guidelines for malaria prevention in travellers from the UK 2019.