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Home Topics Infectious Diseases Infections A-Z Malaria General Information ›  Background information on malaria

Background information on malaria

What is malaria?
Malaria is a serious and potentially life threatening febrile illness caused by infection with the protozoan parasite, Plasmodium. It is transmitted to humans by the bite of the female Anopheles mosquito.

There are four types of malaria that commonly affect humans: Plasmodium falciparum (which is responsible for the vast majority of malaria deaths), Plasmodium vivax, Plasmodium ovale and Plasmodium malariae. There is a fifth type, Plasmodium knowlesi, which is a parasite that usually infects monkeys, but cases of malaria caused by P. knowlesi have recently been reported in humans in South East Asia, and in 2006 the first case was reported in the UK.

How do you catch malaria?
The malaria parasite is transmitted to humans by the bite of an infected female Anopheles mosquito. There are over 420 different species of Anopheles of which around 50 are medically relevant vectors of malaria [4]. Anopheles biting patterns vary depending on world region and species, but malaria transmission takes place most commonly between dusk and dawn. Anopheles gambiae, the principal malaria transmitting mosquito in Africa, is known to be most active indoors after midnight [3]. Malaria is not spread directly from person to person. Rarely, malaria has been known to have been transmitted through breaches in infection control procedures in a healthcare setting [5-8].

Where does malaria occur?
Malaria is endemic in more than 100 countries worldwide, where approximately 3 billion people are at risk of infection. It mainly affects tropical parts of Africa, South and Central America, Hispaniola, Oceania, Asia, and the Middle East. Approximately 250 million cases and 1 million deaths are reported each year; the heaviest burden is in Africa, where the majority of deaths from malaria worldwide occur each year, mostly in children [1]. Malaria does not occur naturally in the UK but travel-associated cases are reported in those who have travelled to or arrived (either as a visitor or migrant to the UK) from malaria-endemic areas. Since 1990, between 1370 and 2500 cases of malaria (caused by all types) have been reported in the UK each year, with between four and 16 deaths (see epidemiological data pages). Occasionally, cryptic cases of malaria are reported in the UK where no travel history or medical procedures have been identified. These cases may occur as a result of an infected mosquito being brought into the UK from a malaria endemic country by plane (airport malaria) or in someone's baggage (baggage malaria) and surviving long enough to bite a nearby person before it dies. See cryptic malaria page for more information.

What are the symptoms of malaria?
Often the first symptom is a non-specific flu-like illness with fever, sweats and chills. Other symptoms can include malaise, myalgia (muscle pain), headache, diarrhoea and cough. Malaria caused by P. falciparum can progress to become a severe and life-threatening illness if not diagnosed and treated promptly, leading to cerebral malaria which can cause coma and death [3].

How long can you have the infection before developing symptoms?
The incubation period of malaria (the time from when the parasite enters the body, to the development of symptoms) varies depending on which Plasmodium species is causing the infection. During this incubation period the parasite undergoes an initial period of development in the liver, after which it infects red blood cells. For P. falciparum, the incubation period is 7-14 days. For P. vivax and P. ovale infection, the incubation period is typically 12-18 days, but can be a lot longer (months or years in some cases) due to a longer liver stage [3].

How can you avoid getting malaria?
Follow the ABCD of malaria prevention below. See the Malaria leaflet, Information for people travelling overseas for more information.

  • Awareness of the risk - check your destination to see if malaria is a risk and visit your GP or your usual travel health advisor in plenty of time (6-8 weeks ideally but it is never too late) for travel health advice before you go.
  • Bite prevention - use an insect repellent containing DEET (N,N-diethylmetatoluamide), wear cover up clothing especially at night when mosquitoes are most active, sleep under a bed net or in an air-conditioned room. More information about bite prevention is available from the National Travel Health Network and Centre (NaTHNaC).
  • Chemoprophylaxis (preventive medication) - there are a number of different types of chemoprophylaxis, and you should speak to your travel health advisor to determine the medication that is most suitable for you and your family. Visit your doctor or travel health clinic well in advance of your departure date (ideally 6-8 weeks), though it is never too late to seek advice and start taking malaria precautions. Make sure you understand how and when to take your tablets. You need to start taking them before you go, continue all the time you are away and also for a period of time when you return. Remember - it is vital that you finish the course of tablets when you get back to make sure you are properly protected. Homoeopathic or herbal remedies do not protect against malaria and must not be used in place of antimalarial tablets. Effective chemoprophylaxis taken correctly can reduce the risk of malaria by around 90%, especially if combined with strict mosquito bite avoidance measures. More information about the options for chemoprophylaxis is available from the ACMP malaria prevention guidelines  and from NaTHNaC.
  • Prompt Diagnosis - although malaria prevention methods are highly effective, they do not provide 100% protection. If you or any of your family has a fever or flu-like illness after being in a country with malaria you must see your doctor urgently. Tell them where you have been and mention malaria. Remember you could still have malaria, even a year after a trip to a malaria-endemic area.

Who is most at risk of catching malaria?
Anyone who visits a malaria-endemic country is at risk of acquiring malaria if they do not take precautions as described above. Even if you grew up or lived in a malaria-endemic country and are now returning to visit your friends or family, you and your family will be at risk. No one has full immunity to malaria. Any partial protection you may have from being brought up in a malarious country is quickly lost when you live in countries with no malaria, so everyone needs to take precautions to avoid getting malaria. Your family are at risk as well. Babies and children, especially those born outside the tropics, can get very sick with malaria very quickly. It is also particularly dangerous for pregnant women, who should avoid visits to malarious areas.

An analysis of malaria deaths over 20 years in the UK by the PHE Malaria Reference Laboratory, which was published in early 2012, has shown that whilst ethnic minority travellers visiting friends and relatives are at particular risk of acquiring malaria, once acquired, the risk for mortality is significantly higher in holiday travellers. There is a strong association between increasing age and mortality, and an inverse relationship between UK regions which treat a lot of malaria, and mortality rates [9]. Therefore elderly travellers should also be considered a particular risk group.

How is malaria treated?
If you suspect that you may have malaria, you should seek urgent medical treatment. Remember malaria can present up to a year after leaving a malaria endemic area. There are several treatment options available for malaria; the option chosen depends on many factors, including any reported drug resistance in the country visited and type of Plasmodium species causing the infection. P. falciparum infection is considered a medical emergency, requiring hospitalisation to assess symptoms and treatment options. Complicated malaria usually requires admission to high dependency or intensive care units and intravenous anti-malarial treatment.

For non P. falciparum infections it is not unusual for treatment to be given on an out-patient basis. Treatment with two types of anti-malarial may be required to treat the acute infection and to clear any P. ovale or P. vivax from the liver. See malaria treatment guidelines for the UK  for more information.

Is malaria catching?
If you acquire malaria abroad and become ill on your return to the UK, you cannot pass the infection on to anyone else. Malaria cannot be passed directly from person to person.

References

  1. WHO Factsheet on malaria. Available online at: http://www.who.int/mediacentre/factsheets/fs094/en/index.html
  2. Chiodini P, Hill D, Lalloo D, Lea G, Walker E, Whitty C and Bannister B.  Guidelines for malaria prevention in travellers from the United Kingdom 2007. London, Health Protection Agency, January 2007.
  3. NaTHNaC health information sheet on malaria.  http://www.nathnac.org/pro/factsheets/malaria.htm
  4. Stürchler MP. Chapter 6: The Vector and Measures Against Mosquito Bites. In: Schlagenhauf P. Travelers' Malaria. London, BC Decker; 2001.
  5. Kim JY, Kim JS, Park MH, Kang YA, Kwon JW, Cho SH et al. A locally acquired falciparum malaria via nosocomial transmission in Korea. Korean J Parasitol 2009; 47 (3): 269-73.
  6. Jain SK, Persaud D, Perl TM, Pass MA, Murphy KM, Pisciotta JM, et al. Nosocomial malaria and saline flush. Emerg Infect Dis 2005; 11 (7):1097-9.
  7. Abulrahi HA, Bohlega EA, Fontaine RE, al-Seghayer SM, al-Ruwais AA. Plasmodium falciparum malaria transmitted in hospital through heparin locks. Lancet 1997; 349 (9044): 23-5.
  8. Moran E, Collins L, Clayton S, Peto T, Bowler IC. Case of cryptic malaria. Commun Dis Public Health 2004; 7 (2): 142-4.
  9. Checkley AM, Smith A, Smith V, Blaze M, Bradley D, Chiodini PL, Whitty CJM. Risk factors for mortality from imported falciparum malaria in the United Kingdom over 20 years: an observational study. BMJ. 2012; 344: e2116. doi: 10.1136/bmj.e2116.

Last reviewed: 16 December 2013