What is malaria?

Malaria is a serious infection. It is common in tropical countries such as parts of Africa, Asia and South America. It is caused by a parasite (germ) called plasmodium that lives in mosquitoes. The parasite is passed to humans from a mosquito bite.

There are four types of plasmodium that cause malaria. These are called Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale and Plasmodium malariae. Plasmodium falciparum is usually the most serious of the four.

Most infections occur in travellers returning to the UK (rather than visitors coming to the UK). The risk of getting malaria is greatest if you do not take your anti-malarial medication or do not take it properly. People who take last-minute holidays and also those visiting friends or relatives abroad have been shown to be the least likely to take their anti-malarial medication.

It is estimated that worldwide there are 300-500 million cases of clinical malaria each year and about 40% of the world's population is at risk of acquiring malaria. Each year around 1,700 people in the UK develop malaria which has been caught whilst abroad. About nine people die from malaria in the UK each year. Malaria can kill people very quickly if it is not diagnosed promptly.

Note: if you feel unwell and have recently visited an area in which there is malaria you should seek prompt medical advice, even if you have taken your anti-malarial medication correctly.

How is malaria transmitted?

The plasmodium parasite is usually transmitted by a particular species of mosquito, which is the anopheles mosquito. If a female anopheles mosquito bites a person who is infected with malaria, the mosquito can then carry the plasmodium parasite and then spread it to others when it bites and feeds from other people's blood.

When the plasmodium parasite enters your blood, it travels to your liver and then re-enters the blood stream where it can invade your red blood cells. Eventually, these infected red blood cells burst which leads to them releasing even more of the tiny parasites into your blood. These infected red blood cells tend to burst every 48-72 hours. Each time they burst, you will usually experience an episode of chills, fever and sweating.

What are the symptoms of malaria?

There are two general types of malaria: benign and malignant. Benign malaria is milder and relatively easy to treat. Malignant malaria can be very severe and can sometimes be fatal.

Symptoms of malaria usually occur between one to four weeks after the initial mosquito bite. However, in some cases, depending on the type of plasmodium you are infected with, it can take up to a year before any symptoms start to show. This means that you should suspect malaria in anyone with a feverish illness who has travelled to a malaria area within the past year, especially in the previous three months.

Benign malaria

The most common symptom of benign malaria is a high fever. However, the absence of fever in an ill person does not exclude the diagnosis of malaria.

Other symptoms of benign malaria may include:

• Headaches, muscle pains, abdominal pains, cough, feeling more tired than usual and feeling generally unwell.
• Children are more tired and can have diarrhoea and/or vomiting.
• If you have taken anti-malarial medication then you may have different symptoms (for example backache) if you have malaria.
• The fever in most people has no specific pattern and may present 1-2 days after the symptoms start. If the malaria infection becomes established, then malarial symptoms can come in cycles, occurring every 2-3 days (see above).

Malignant malaria

Malignant malaria is caused by Plasmodium falciparum. Malignant malaria usually begins with similar symptoms to benign malaria, but will often lead to your developing further complications, such as breathing problems, liver failure and shock. Malignant malaria can also affect the brain and central nervous system which can even lead to death.

Note: if you are pregnant then you are at particular risk of severe malaria, and should, ideally, not go to malaria risk areas. This is because your immune system can be weaker during your pregnancy. If you are pregnant and have malaria, you may pass the infection on to your baby.

How is malaria diagnosed?

If you think you may have malaria, then you need to seek medical advice without delay. If you have travelled to an area in which there is malaria in the past year then you may be at risk of this disease, even if you took anti-malaria medication when you were abroad.

Your doctor will perform a blood test. The blood sample will be sent to the laboratory and will be examined for the presence of the malaria parasite. The type of malaria causing the infection will also be determined. If the first blood test is negative but your doctor suspects you have malaria, then you may be asked to have another blood test taken a couple of days later.

How is malaria treated?

If malaria is promptly diagnosed and treated, most people make a full recovery. Malaria is normally treated using anti-malarial medicines. There are different types of these medicines available.

The type of medicine prescribed and the duration of treatment can vary from person to person. It depends on a various factors such as the type of malaria that you have, if you have taken any anti-malarial medication when you were travelling, and the severity of your symptoms. If your symptoms are mild then you will be treated at home. However, if you have Plasmodium falciparum malaria then it is very likely you will be treated and monitored in hospital.

Some people are given more than one type of medication or an alternative medication if they develop side-effects to a medication. Resistance to antimalarial drugs has spread rapidly over the past few decades, especially to Plasmodium falciparum. This means that newer drugs or a combination of drugs may be given.

If the first anti-malarial medicine that you are prescribed fails to improve your symptoms, you may have to try a variety of other medicines as part of your treatment. You may find that your treatment for malaria leaves you feeling very weak and tired for several weeks afterwards.

Travellers going to remote places far from medical facilities sometimes take emergency medication with them. This can be used to treat suspected malaria until proper medical care is available.

How can malaria be prevented?

There is an "ABCD" of malaria prevention. This is:

• Awareness of risk of malaria.
• Bite prevention.
• Chemoprophylaxis (taking anti-malarial medication regularly and exactly as prescribed).
• prompt Diagnosis and treatment.

See separate leaflet called 'Malaria Prevention' for more detail.

Further Information

Malaria Reference Laboratory (MRL)
London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT
Web: www.malaria-reference.co.uk
The MRL website provides information and advice on malaria and its prevention.

MASTA
Web: www.masta-travel-health.com
MASTA provide travel health advice on anti-malarial treatment.

The National Travel Health Network and Centre (NaTHNaC)
Web: www.nathnac.org
NaTHNaC provides travel health information for both health professionals and the public.