Malaria is an infectious disease that kills an average of more than one million people every year, mostly infants, young children, and pregnant women. Most of those deaths are in Africa.

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(CBC)

Every 30 seconds, a child dies of malaria.

But you don't have to be a child or a pregnant woman to be infected. Every year, more than 500 million people become severely ill from the disease.

According to the World Health Organization, malaria is endemic — or constantly occurring — in more than 100 countries around the world. Most cases occur in sub-Saharan Africa, but parts of Asia, Latin America, the Middle East and Europe are also affected.

People from malaria-free countries are especially vulnerable to the disease when they travel to areas where malaria is present. They have little or no immunity to the disease and are often misdiagnosed when they return home and begin showing symptoms.

Marking the first World Malaria Day held on Friday, April 25, 2008 United Nations Secretary-General Ban Ki-moon announced an initiative to offer indoor spraying and bed nets to "all people at risk, especially women and children in Africa."

Only about two per cent of African children currently sleep under insecticide-treated bed nets — one of the most effective tools in the prevention of malaria. Ban is calling for coverage for an additional 500 million people.  The plan will also ensure public health facilities have access to effective malaria treatment and diagnosis.

In December 2010, the World Health Organization released a report saying scaled up malaria control programs since 2008 has helped to protect more than 578 million people in sub-Saharan Africa. The number of deaths as a result of malaria is estimated to have decreased from 985,000 in 2000 to 781,000 in 2009, according to the report.  

What causes malaria?

The disease is caused by several species of single-celled parasite of the genus Plasmodium, and it is transmitted mostly commonly by mosquitoes.

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Scientist James Mutunga who specialises in mosquito research, holds up a tube containing mosquito larvae to be taken to a laboratory and tested for malaria, Karatina, Kenya, Nov. 7, 2006. ((Kirsty Wigglesworth/Associated Press))

Infected female mosquitoes carry the spores of the parasite. When a mosquito bites, it can transfer the spores to a person through its saliva. The spores collect in the person's liver and multiply there. Some species of the parasite can remain dormant in the liver for several months.

From there, the spores divide and enter red blood cells, where they multiply even more, sometimes bursting out of the blood cells. The waves of fever every few days that are characteristic of the disease are caused by the parasites bursting out of blood cells simultaneously.

There are four types of malaria that infects people:

  • Plasmodium falciparum. 
  • P.vivax.
  • P.malariae.
  • P.ovale.

P.falciparum and P.vivax are the most common. P.falciparum is by far the most deadly type of malaria infection.

What are the most common symptoms of malaria?

Symptoms of malaria include:

  • Headache and fever.
  • Chills.
  • Muscle and joint pain. 
  • Nausea and vomiting. 
  • Convulsions.

Symptoms normally begin showing up 10 to 15 days after infection. If the person is not treated promptly, the disease can rapidly worsen, turning into severe illness that can be fatal.

The symptoms of malaria can be mistaken for those of other diseases, so a diagnosis requires a blood test.

Health Canada warns that if you unexpectedly develop fever within three months of returning from a malaria-endemic area, see a doctor immediately. Consider yourself a medical emergency. Get your blood tested and repeat those tests within 12 to 24 hours if your symptoms persist.

Am I at greater risk of developing malaria at specific times of the year?

It depends where you travel. Malaria is always a risk in certain tropical countries, especially in sub-Saharan Africa.

But malaria transmission can occur seasonally as well, differing in intensity and regularity depending on local factors such as rainfall patterns, proximity of mosquito breeding sites and mosquito species.

You should monitor the Public Health Agency of Canada's travel advisories website for information on problem areas before you travel.

How is malaria treated?

The treatment of malaria depends on several things: the species of parasite, the severity of the infection and the age of the person infected. In some parts of the world, parasites have become resistant to some of the drugs used in treatment.

Almost all malaria can be completely cured if identified and treated early. But if left untreated, you can go from being asymptomatic to severely ill very quickly. Death can occur within 36 to 48 hours.

The types of drugs used will vary depending on where you've been, which parasite has infected you and how sick you are.

How can malaria be prevented?

Funding for malaria control appeared to have levelled off in 2010 at an estimated at $1.8 billion US a year, compared with the estimated more than $6 billion US needed to fully control malaria, WHO said.

Current anti-malaria efforts are focused on providing people in high-risk areas with protective nets, as well as widespread spraying of insecticides, providing diagnostic services and effective drugs for treatment.

One of the problems with insecticides is that mosquitoes develop tolerances. The more insecticides are used, the less effective they can be.

Dr. Andrew Read, a professor of biology and entomology at Penn State University, has proposed smarter use of pesticides to make them more effective. His research suggests that we can exploit what we know about the life cycle of both the mosquito and malaria parasite to use pesticides smarter. The trick is targeting only the older mosquitoes, which are the ones carrying infectious parasites, but are also the most vulnerable.

Read says it's the older mosquitoes that are dangerous to human health. Sparing younger mosquitoes means you're not giving them the chance to develop resistance to insecticides. When they get older and become a threat to human health, they are more likely to be killed by insecticide.

Read says older mosquitoes can be targeted by diluting current pesticides.

"We think we can take the existing insecticides and dilute them down to the point where they don't kill the young ones but still kill the old ones and that would give this benefit," Read told CBC Radio's Quirks & Quarks. "You could also develop new chemicals that just kill the old mosquitoes. And old mosquitoes are an easy target — they are like humans, they're more frail, more delicate with age. They are much easier targets."

What can I do to protect myself?

The most effective strategy for preventing malaria infection is to avoid being bitten by infected mosquitoes:

  • Stay indoors from dusk to dawn, when mosquitoes are biting most.
  • Wear clothing that reduces the amount of your exposed skin.
  • If you are out between dusk and dawn, wear light-coloured long-sleeved shirts, long pants, socks and shoes.
  • Impregnate all clothing with an insecticide such as 0.5% permethrin to make them repellant. 
  • Sleep under a mosquito net impregnated with permethrin. 
  • Use DEET-based insect repellents.

When travelling in areas where malaria is endemic, children are at higher risk of infection than adults. For children, sparingly apply DEET in a concentration of not more than 10 per cent to exposed surfaces only. Wash it off after your child comes indoors.

While there is no vaccine for malaria, there are antimalaria medications available that can reduce the risk of developing symptoms of the disease. These medications will not provide 100 per cent protection against the disease.