Malaria - including symptoms, treatment and prevention

Malaria is caused by a parasite called Plasmodium. There are 5 species of Plasmodium which infect humans:

  • Plasmodium vivax
  • Plasmodium falciparum
  • Plasmodium malariae
  • Plasmodium ovale
  • Plasmodium knowlesi which is less common.

Of these, Plasmodium falciparum infection is the most severe and can cause death in up to 1 in 10 cases. Pregnant women and children are especially at risk. Other types of malaria are less severe but still may cause death. However, malaria can be prevented and cured if cases are found early.

Malaria is a notifiable condition1

How malaria is spread

The parasite is transmitted to humans by the bite of infected female Anopheles species mosquitoes.

The parasites multiply in the liver and the bloodstream of the infected person. The parasite may be taken up by another mosquito when it bites an infected person. The mosquito is then infected for the duration of its life and can infect other humans when it bites them.

Occasionally malaria is transmitted by blood transfusion. Read more about pre-donation screening for malaria. Malaria can be transmitted from a mother to an unborn baby.

Malaria occurs in most tropical and sub-tropical areas of the world, including:

  • Africa
  • Central and South America
  • Asia, including Southeast Asia
  • Papua New Guinea
  • western Pacific islands.

Australia has not had local malaria spread since 1981. However, the Anopheles mosquitoes that can carry malaria are still present in northern Australia, and several hundred cases occur each year in travellers entering Australia from other countries.

Tourists often get severe illness because they have had no previous exposure to malaria and no resistance to the disease.

Signs and symptoms of malaria

Symptoms can be mild or life-threatening.

Symptoms of malaria may include:

  • fever, which may come and go every 2-3 days, or may be constant
  • chills
  • profuse sweating
  • malaise (feeling of unwellness)
  • muscle and joint pain
  • headache
  • confusion
  • nausea
  • loss of appetite
  • diarrhoea
  • abdominal pain
  • cough
  • anemia.

Plasmodium falciparum may cause kidney, liver and/or lung failure, or cerebral malaria, a serious complication resulting from inflammation of the brain that may cause coma.

Diagnosis of malaria

Diagnosis is made by a blood test – sometimes it is necessary to repeat the test as the parasites can be difficult to detect.

Incubation period

(time between becoming infected and developing symptoms)

Varies with the type:

  • P. falciparum: 9 to 14 days
  • P. vivax: 12 to 18 days but some strains may have an incubation period of 8 to 10 months or longer
  • P. ovale: 12 to 18 days
  • P. malariae: 18 to 40 days
  • P. knowlesi 9 to 12 days.

These periods are approximate and may be longer if the person has been taking drugs taken to prevent infection.

If an infection is not fully treated with anti-malarial medicine, it can relapse months or years later, when parasites emerge from the liver back into the bloodstream.

Infectious period

(time during which an infected person can infect others)

Direct person-to-person spread does not occur.

A person remains infectious to mosquitoes as long as the parasites are present in the blood. This may be several years if adequate treatment is not given. Parasites disappear from the blood within a few days of commencing appropriate treatment. Mosquitoes remain infected for life.

Treatment for malaria

Specific antimalarial treatment is available and must always be started as soon as malaria is diagnosed. There is increasing resistance to currently available drugs and treatment should be carried out by an infectious diseases specialist or other expert in the field.

Prevention of malaria

  • Travellers to areas with malaria are usually advised to take preventative anti-malarial drugs and protect themselves from mosquito bites.
  • Exclusion from childcare, preschool, school or work is not necessary. Cases should avoid being bitten by mosquitoes while they are unwell. 
  • Personal protection and the environmental management of mosquitoes are important in preventing illness. See Mozzies Suck for tips to on how to protect yourself.

Travel in countries where there is malaria

Extensive international programs are undertaken in malarious countries to try to control this disease. For travellers, the following advice is given:

  • See a travel medicine expert 4-6 weeks before you go to get specific advice for the places you will be visiting.
  • Pregnant women should try to avoid travel to countries with malaria if possible, given the risk of miscarriage or early labour if they get infected.
  • Always take malaria prevention drugs exactly as prescribed and take the full course (which usually includes before, during and after travel). Be aware of their potential side effects.
  • Protect yourself from mosquito bites. Travel medical centres have good information on how to do this.
  • Be aware that no preventive measures are 100% effective, so always seek medical attention immediately if you develop a fever while travelling in, or after return from, a country where malaria occurs.
  • Always give your doctor the information about your travel if you become sick within 12 months of returning from a country with malaria.

Useful links

1 – In South Australia the law requires doctors and laboratories to report some infections or diseases to SA Health. These infections or diseases are commonly referred to as 'notifiable conditions'.