Malaria: Causes, Symptoms & Treatment

Malaria is a disease caused by a parasite that gets passed into the bloodstream of humans by the bite of an infected mosquito. Only the Anopheles species of mosquito can transmit malaria, and mosquitoes pick up the parasite from biting a person already infected with the illness. 

People with malaria typically get very sick and experience a high fever, teeth-rattling chills and muscle aches. If caught early and treated, severe illness and death can usually be prevented. 

Malaria is very rare in the United States, where about 1,700 cases and five deaths occur each year, mostly in immigrants and travelers returning from countries where the disease is common, according to the Centers for Disease Control and Prevention (CDC). 

However, in many developing countries, malaria is a leading cause of death and disease, where children under age 5 and pregnant women are the hardest hit groups. In 2017, there were 219 million cases of malaria worldwide and about 435,000 deaths, according to the World Health Organization (WHO). The majority of cases were in tropical and subtropical countries. 

Common malaria regions include large areas of Africa south of the Sahara desert, Southeast Asia, Central and South America, Haiti and the Dominican Republic, Eastern Europe and the South Pacific, according to the American Academy of Family Physicians.

It's difficult to control malaria worldwide because parasites tend to stay in our bodies, and the immune system is not very effective at clearing them, said Dr. Edward Ryan, director of global infectious diseases at Massachusetts General Hospital in Boston. In addition, some species of Anopheles mosquitoes are hard to wipe out, he said. 

By 1949, the U.S. eliminated malaria, according to the CDC. The country implemented a coordinated public health effort in southern states that involved spraying insecticides and removing mosquito breeding sites, Ryan said. The growing, widespread use of air conditioning and screens on doors and windows also helped keep mosquitoes outside of homes, he said. 

How do you get malaria? 

Malaria is transmitted by the bite of an infected Anopheles female mosquito, which passes on the Plasmodium parasite to people. 

Anopheles mosquitoes thrive in areas with warm temperatures, humid conditions and high rainfall, according to the University Corporation for Atmospheric Research in Boulder, Colorado. 

Five species of Plasmodium parasites can infect people with malaria, but some species cause more serious problems than others. The Plasmodium falciparum parasite is the one most likely to cause severe, life-threatening illness if the infection is not promptly treated. 

When the malaria parasite enters a person's body, it travels to the liver, where it multiplies and matures. Parasites are then released into the bloodstream, where they invade and infect red blood cells. 

The parasites continue multiplying and infecting other red blood cells, and these cells eventually rupture and release toxins, causing a person to experience flu-like symptoms. As the disease progresses, the liver and spleen (which filters and stores blood) can enlarge.

Related: 8 Awful Parasite Infections That Will Make Your Skin Crawl

With severe malaria, the blood inside the body sludges, or piles up and sticks to blood vessel walls, so it doesn't flow normally, Ryan told Live Science. A person may die of the disease because the sludging blocks blood vessels to organs, such as the lungs, brain or kidneys, causing damage, he said. 

Malaria is not spread from person to person. But in very rare instances, it can be transmitted by a blood transfusion containing the parasite, by the sharing of drug needles or from an infected mother to her baby during pregnancy or delivery.

Two groups most vulnerable to malaria are young children, who have not yet developed immunity to the disease; and pregnant women, whose immunity has decreased because they are expecting, according to the CDC. 

Other high-risk groups are visitors from countries with no malaria and therefore, no immunity, as well as travelers who grew up in malaria regions, but moved away for long periods of time and lost their partial immunity to the parasite. 

Symptoms

Symptoms of malaria may develop a week or two after a person is bitten by an infected mosquito, or they may show up several months or more after exposure, according to the National Organization for Rare Diseases.

Early symptoms may resemble the flu, such as fever, chills, headache and muscle aches, Ryan said. Other early signs include tiredness, nausea and vomiting. Then, a person may experience a high fever and teeth-rattling chills, followed by heavy sweating and exhaustion when the fever breaks. 

Malaria can rapidly become a serious, life-threatening disease. According to the CDC, some complications of severe malaria, which is more common with P. falciparum infections, may include:

• Liver and kidney failure
• Mental confusion, convulsions and coma 
• Severe anemia from destruction of red blood cells
• Jaundice (yellowing skin and eyes) from a loss of red blood cells
• Death

Diagnosis and treatment

A simple blood test is used to detect the malaria parasite under a microscope, Ryan said. The blood test confirms malaria parasites are present and identifies the species causing illness. 

If the illness is diagnosed early and treated, it's totally curable and all malaria parasites can be cleared from the body, he said. Both intravenous and oral medicines are available to treat malaria and remove the parasite from the blood. 

The majority of people with malaria in the U.S. are hospitalized, but the length of stay depends on which species of the parasite an individual has been infected with and how healthy someone was to start, Ryan said. A patient will receive anti-malarial medications to fight the parasite and will be monitored to ensure the level of infection is falling. 

Some malaria drugs may not be effective because parasites have become increasingly resistant to them, making it difficult to control the disease worldwide, the CDC reports. 

Prevention

When visiting malaria-zone countries, travelers need to consider the time they will spend in each destination, the type of travel (air-conditioned hotels versus rural villages) and the season (some locations have year-round malaria risk, while others have high and low periods), Ryan said. 

Minimize risk by taking the following precautions: 

• Take appropriate anti-malarial medications — before, during and after the visit —which are highly effective at preventing the disease, Ryan said. 
• Apply insect repellent. Choose products containing DEET when applying the repellent on exposed skin. Spray pyrethrin, an insecticide, on clothing. 
• Limit outdoor activities between dusk and dawn — the peak feeding times for Anopheles mosquitoes. Wear long-sleeved shirts and pants to cover skin. 
• Use bed netting. If visiting rural villages, sleep under insecticide-treated bed netting and spray insecticides indoors to keep mosquitoes away. 

Additional resources: 

• Find answers to frequently asked questions about malaria, from the CDC. 
• Traveling abroad? Learn from the CDC whether you're visiting a country where malaria is found.
• Read about the global effects of malaria, as detailed by the World Health Organization.