Malaria - the disease

This factsheet is for people who have malaria, or who would like information about it.

Malaria is an infectious disease commonly found in tropical areas such as sub-Saharan Africa, Central and South America, the Indian subcontinent, South East Asia and the Pacific Islands (these are known as malarious regions). It's caused by a parasite called Plasmodium, which is passed to people through bites from mosquitoes carrying the parasite.

About malaria

There are two categories of malaria.

• Malignant malaria (also known as falciparum malaria) causes symptoms within six months of infection and can be mild or severe. It's caused by one type of malaria parasite, Plasmodium falciparum.
• Benign malaria is less severe but may have a dormant stage of up to a year and can cause relapses. This is mostly caused by one of the other three types of malaria parasite.

Around 1,500 people a year in the UK get infected with malaria when abroad.

Symptoms of malaria

The first symptoms of malaria are like having the flu. You may have:

• a headache
• aching muscles
• a tummy ache, diarrhoea and vomiting – especially in children
• a lack of energy
• loss of appetite
• a cough

A day or so later, you may get a fever. Some people have malaria attacks – these have three stages: shivering, hotness and sweating.

Symptoms can appear any time from a week to 14 days after you’re bitten by a mosquito carrying the malaria parasite. The time it takes your symptoms to appear (the incubation period) can vary depending on the type of parasite that the mosquito was carrying, whether or not you have partial immunity or if you have taken any anti-malaria tablets.

• If a mosquito carrying the P. falciparum parasite bites you, symptoms usually appear within six months of the bite, and most commonly start within a month.
• If a mosquito carrying the Plasmodium vivax, Plasmodium ovale or Plasmodium malariae parasite bites you, symptoms appear typically within 12 to 18 days. However, the parasite can lay dormant in your liver and not become active causing symptoms until months later. These parasites may also cause your symptoms to return.

If you have an illness with a fever and have travelled to a region with malaria within the last year, visit your GP. You can still catch malaria even if you have taken antimalarial medicines correctly.

Complications of malaria

If you are infected with P. falciparum, malaria can progress to a more severe form (also called complicated malaria). Complications can affect your brain, kidneys, blood and lungs. They can develop within hours or days of your first symptoms and can be fatal within 24 hours.

Symptoms of severe malaria can include:

• jaundice – yellowing of your skin or the whites of your eyes
• difficulty breathing
• fluid on the lungs – pulmonary oedema
• feeling light-headed or shaky (symptoms of low blood sugar)
• bleeding
• pale skin
• fits
• loss of consciousness

It's important to seek urgent medical attention if you suspect you have severe malaria. Always tell your doctor where you have travelled. Complications are likely to be more severe in pregnant women, children, older people and people who have a weakened immune system, such as those who have HIV/AIDS.

Causes of malaria

Malaria is caused by an infection with a parasite called Plasmodium that is passed to people through mosquito bites.

Malaria parasite

You can catch malaria if a female anopheles mosquito bites someone carrying the malaria parasite and then bites you, passing the parasite on to you.

There are four main types of Plasmodium parasite that infect humans.

• P. falciparum – this is the only parasite that causes malignant malaria. It causes the most severe symptoms and results in the most deaths.
  
• P. vivax – this causes benign malaria with less severe symptoms than P. falciparum. P. vivax can stay in your liver for years and symptoms can return.
  
• P. ovale – this causes benign malaria and can stay in your blood and liver for many years without causing symptoms.
  
• P. malariae – this causes benign malaria and is relatively rare.

About eight in 10 UK travellers who get malaria are infected with P. falciparum. Most of the other people are infected by P. vivax, and just a few are infected with the other two species. You can get infected with more than one type of Plasmodium parasite. Each parasite causes a slightly different type of illness.

Parasite lifecycle

The malaria parasite passes through your blood into your liver, where it grows and develops.

After it has completed its development, it travels back into your bloodstream and eventually attacks your red blood cells, which you need to carry oxygen around your body. You will then get symptoms of malaria.

Diagnosis of malaria

Your GP will ask about your symptoms and examine you. He or she may also ask you about your medical history and which countries or regions you have visited within the last year, including any stopovers.

Malaria is a medical emergency. If your GP suspects that you have malaria, he or she may refer you to your local hospital to have a blood test to confirm if you have malaria parasites in your blood and what type of parasite you have been infected with. You will need to have at least three blood tests over one to three days as the levels of malaria parasite in your blood can vary. For example, if you have taken antimalarial medicines, the levels of parasite may be too low to detect. If you are still taking antimalarial medicines while being investigated, your doctor may ask you to stop these so that they don’t interfere with any blood tests you may have. Repeating blood tests can help to confirm if you have malaria.

If you’re diagnosed with malaria, your doctor will notify the public health authorities. It’s also important for you to let any travel companions know to ensure they get tested too. They may also be infected but not know as he or she may not develop any symptoms for some time.

Treatment of malaria

There are a number of medicines that can treat malaria but you must start your treatment as soon as possible. Certain medicines don't work for malaria from some parts of the world – your doctor will ask where you have been and take this into account.

Some malaria medicines are also used to help prevent the infection. But if you have taken a medicine to prevent malaria, you can't take the same one again to treat it. So it's important to tell your doctor about any antimalarial medicines you have taken – take the medicine packaging to your GP appointment if you can.

Medicines

Treating mild P. falciparum malaria

There are three main treatments for mild P. falciparum malaria.

The standard treatment for mild P. falciparum malaria in the UK is quinine tablets followed by a second medicine, which may be:

• doxycycline – for most adults
• clindamycin – for most pregnant women and children
• sulfadoxine with pyrimethamine (Fansidar)

Alternative medicines for P. falciparum malaria include:

• artemether with lumefantrine (Riamet)
• atovaquone with proguanil (Malarone)
• artesunate

If you have P. falciparum malaria, you will usually need to stay in hospital to be monitored. This is because malaria can rapidly progress to a more severe infection.

Treating severe P. falciparum malaria

The standard treatment for severe P. falciparum malaria is quinine, which will be injected directly into a your bloodstream through a vein (intravenously). An alternative treatment is artesunate. Once you're well enough, you can have the rest of your treatment as tablets that you swallow.

If you have severe P. falciparum malaria, you need to be monitored carefully and treated for any complications. The severity of malaria usually depends on how many of your red blood cells are infected.

Treating other types of malaria

The standard treatment for other types of malaria is chloroquine tablets (eg Avloclor, Malarivon, Nivaquine). You can take chloroquine if you're pregnant.

If you have malaria caused by P. vivax and P. ovale, you will need treatment to stop the infection coming back because parasites can stay in your liver. Primaquine is the usual medicine. If you’re pregnant, your doctor will usually advise that you wait until you have given birth before you take this.

If your illness is mild, you will probably be able to take your medicines at home. However, you will need to go to hospital if you develop complications or need medication through an intravenous drip.

Treating complications

If you’re diagnosed with severe malaria your doctors will monitor your kidneys, blood pressure, fluid balance (how much you drink and how much urine you pass), and your blood sugar levels as well as treat any complications. For example, you may be given a glucose drip to help raise your blood sugar levels if they drop.

Special considerations

Acquired immunity

If you're born in an area with malaria, you may develop a form of immunity to the infection. It never gives complete protection but it can reduce your risk of developing severe malaria. However, if you leave the area for six months or more you may lose this immunity so you will need to take antimalarial medicines if you return or go to another area with malaria.

If you're pregnant

Complications of malaria are more likely if you’re pregnant. Malaria in pregnancy is also associated with miscarriages or stillbirths.

If you have malaria and are pregnant, you will need to take quinine. Scientific evidence shows that quinine is safe in pregnancy, although it can increase the risk of you having low blood sugar levels. Your doctor will monitor you and your baby for any signs of complications. He or she may decide you need to have your baby early if this is the safest option for you and your baby. 
 

For answers to frequently asked questions on this topic, see Common questions.

For sources and links to further information, see Resources.