Malaria is a disease caused by a parasite that is transmitted person-to-person by the bite of an infected Anopheles mosquito. These mosquitoes are present in the tropics and subtropics in almost all countries.
Malaria is a disease caused by a parasite that is transmitted to humans by the bite of an infected Anopheles mosquito. These mosquitoes are found in the tropics and subtropics in almost all countries. Nearly all cases of malaria in the U.S. are in people who have traveled internationally. Malaria is considered an entirely preventable and treatable disease. Treatment ensures elimination of the parasite from the blood, which prevents chronic or severe disease.
After the parasites enter the body by a mosquito bite, they disappear from the circulating blood within an hour and gather in the liver. After several days, infected red blood cells (RBCs) emerge from the liver and infect other RBCs.
These are the species of Plasmodium (single-celled parasites) that can infect humans and cause illness:
Plasmodium falciparum (or P. falciparum)
Plasmodium malariae (or P. malariae)
Plasmodium vivax (or P. vivax)
Plasmodium ovale (or P. ovale)
Plasmodium knowlesi (or P. knowlesi)
Generally, falciparum malaria is the most potentially life-threatening. Patients with severe falciparum malaria may develop liver and kidney failure, convulsions, and coma. Infections with P. vivax and P. ovale may cause less serious illness, but the parasites can remain dormant in the liver for many months, causing a reappearance of symptoms months or even years later. P. knowlesi can be transmitted from Southeast Asian monkeys to humans by the bite of an infected mosquito. Studies suggest it is more widespread among humans in this region--so there may be human-to-human transmission after a bite from an infected mosquito.
The risk of acquiring malaria depends on:
Duration of travel
Place where the traveler will spend the evenings and nights. (Anopheles mosquitoes bite most often during nighttime hours from dusk to dawn.)
Early stages of malaria may be similar to the flu. The following are the most common symptoms of malaria. However, each individual may experience symptoms differently. Symptoms may include:
Sometimes vomiting, diarrhea, and coughing
Symptoms of malaria usually appear from seven to 30 days after the infectious mosquito bite and may resemble other medical conditions. Always consult your doctor for a diagnosis.
In addition to a complete medical history and physical exam, diagnostic procedures for malaria may include blood work to rule out other possible infections. Infected RBCs from a person's blood sample can also often be seen under the microscope.
Malaria can be prevented by the use of antimalarial drugs and use of protection measures against mosquito bites.
Medications. When planning to travel to an area where malaria occurs, talk with your doctor well in advance of your departure. Drugs to prevent malaria can be prescribed, but travelers from different countries may receive different recommendations, reflecting differences in treatment protocols as well as availability of medicines in different countries. Travelers visiting only cities or rural areas where there is no risk of malaria may not need preventive drugs, but an exact itinerary is necessary to determine what degree of protection may be needed.
There are several medications recommended for prevention of malaria in travelers. Determining which medication is best depends on several factors, such as your medical history and the amount of time before your scheduled departure. Strict adherence to the recommended doses and schedules of the antimalarial drug selected is necessary for effective protection. These medications must be started before you arrive at your destination and continued for a specific number of days or weeks after your return, depending on which medication is prescribed.
Protection from mosquitoes. Be aware that you are still at risk for malaria even with the use of protection.
To avoid mosquito bites, the CDC recommends the following:
Apply insect repellent to exposed skin. The recommended repellent contains 20 to 35 percent N,N-Diethyl-meta-toluamide (DEET).
Wear long-sleeved clothing and long pants if you are outdoors at night.
Use a mosquito net over the bed if your bedroom is not air-conditioned or screened. For additional protection, treat the mosquito net with the insecticide permethrin.
Spray an insecticide or repellent on clothing, as mosquitoes may bite through thin clothing.
Spray pyrethrin or a similar insecticide in your bedroom before going to bed.
Note: According to the CDC, vitamin B and ultrasound devices do not prevent mosquito bites.
Specific treatment for malaria will be determined by your doctor based on:
Your overall health and medical history
Extent of the condition
Your tolerance for specific medications, procedures, or therapies
Expectations for the course of the condition
Your opinion or preference
Travelers who become ill with a fever during or after travel in a malaria risk area should seek prompt medical attention and should inform their doctors of their recent travel history. Neither the traveler nor the doctor should assume that the traveler has the flu or some other disease without completing a laboratory test to determine if the symptoms are caused by malaria.
Malaria symptoms can develop as early as six to eight days after being bitten by an infected mosquito or as late as several months after departure from a malarious area, after antimalarial drugs are discontinued. Malaria can be treated effectively in its early stages, but delaying treatment can have serious consequences. Important, current information about prevention and precautions is available online from the CDC.
The following related clinical trials and research studies are currently seeking participants at Massachusetts General Hospital. Search for clinical trials and studies in another area of interest.