The parasite invades red blood cells and is transported to the liver. Symptoms appear after 10-15 days and include fever, fatigue and vomiting.
Five types of the malaria parasite cause infection in humans, with Plasmodium falciparum causing the most severe infections.
Avoiding mosquito bites is the best malaria prevention. No-one should be prescribed antimalarial medicine without learning how to prevent mosquito bites.
Travellers who return home with malaria have often not understood the consequences of not using insect repellents and antimalarial medicine for fear of side effects.
How to avoid mosquito bites:
- Do not stay outdoors after sunset without protection
- Protect your body with socks, long trousers and long-sleeved clothing (can be impregnated with insect spray) after sunset in areas with malaria, or all day in areas with dengue fever.
- Use repellents - diethyltoluamide (DEET) or otherwise on the skin when staying outdoors.
- Sleep under mosquito nets indoors or outdoors. Permethrin-impregnated mosquito nets are recommended in areas of high malaria risk.
- Small children can be effectively protected by an impregnated mosquito net over the bed, pram or playpen. Baby baskets can be lined with mosquito-proof fabric. Use insect repellents with care.
- Mosquito-free house: use mosquito netting, preferably impregnated, on doors, windows and air vents. Use insect spray in the bedroom a few hours before going to sleep. Do not turn on the light before doors and windows are closed. Hotel rooms with air conditioning are usually mosquito-free.
- Listen to local information on malaria incidence.
Assessment of risk
Length of stay
The risk of infection with malaria increases with length of stay in a malaria area, more than four weeks is considered to be long-term.
Risk of malaria-infected mosquitoes
The number of mosquitoes infected with the malaria parasite varies by region. The risk is highest during and after the rainy season.
Risk of drug-resistant malaria
In some parts of the world, parasites are becoming resistant to many of the common antimalarial medicines. The problem is greatest where P. falciparum has developed resistance to chloroquine and mefloquine, currently in the border area between Thailand, Cambodia and Myanmar.
Immigrants visiting their former homeland
Immigrants who return to Norway after visiting their former homeland are the largest group diagnosed with malaria. They are often unaware of their own and their children's lack of immunity and do not consider the need for malaria prevention. Antimalarial medicine in addition to mosquito bite prevention may be recommended in some malaria areas where short-stay tourists are only recommended to adopt mosquito bite prevention (for example, Pakistan and India).
Backpackers and travellers who engage in outdoor activities (hiking, paddling, etc.) in areas where mosquitoes thrive are particularly at risk. They may need to take antimalarial medicine in malaria areas where short-stay tourists are only recommended to adopt mosquito prevention methods.
Pregnant women should avoid travelling to malaria areas unless absolutely necessary. If pregnant women choose to travel to malaria areas, they should use adequate protection.
Children under 5 are generally more at risk of getting severe malaria, which may be fatal in some cases.
People with immunodeficiency disorders may be more susceptible to developing severe malaria if they are infected. This also applies to people using immunosuppressive drugs. They should be made aware of the possible increased risk with information about the importance of mosquito bite prevention and antimalarial medicine.
Travellers who intend to stay more than a day's journey away from available health care in a highly endemic malaria area may need to take an emergency kit for self-treatment.