Malaria
What is Malaria?
Malaria is a disease caused by a parasite that lives part of its life in humans and part in mosquitoes. This viral infection remains one of the major killers of humans worldwide, threatening the lives of more than one-third of the world’s population. Malaria thrives in the tropical areas of Asia, Africa, and South and Central America, where it strikes millions of people. Sadly, as many as 2.7 million of its victims, mostly infants and children, die yearly. Although malaria has been virtually eradicated in the United States and other regions with temperate climates, it continues to affect hundreds of people in this country every year.
In 2000, health care workers reported 1,400 cases of malaria to the U.S. Centers for Disease Control and Prevention (CDC). Malaria in the United States is typically acquired during trips to malaria-endemic areas of the world and therefore is often called travelers’ malaria. During the past 10 years, CDC has documented local cases of malaria in states as varied as California, Florida, Texas, Michigan, New Jersey, and New York. In the summer of 1999, one highly publicized case occurred at a Boy Scout camp on Long Island, New York, where two boys were infected by mosquitoes.
Symptoms of Malaria
Malaria typically produces a string of recurrent attacks, or paroxysms, each of which has three stages—chills, followed by fever, and then sweating. Along with chills, the person is likely to have headache, nausea, and vomiting. Within an hour or two, the person’s temperature rises, and the skin feels hot and dry. Then, as the body temperature falls, a drenching sweat begins. The person, feeling tired and weak, is likely to fall asleep.
The symptoms first appear some 10 to 16 days after the infectious mosquito bite and coincide with the bursting of infected red blood cells. When many red blood cells are infected and break at the same time, malaria attacks can recur at regular time periods—every 2 days for P. vivax malaria and P. ovale, and every 3 days for P. malariae. With P. vivax malaria, the patient may feel fine between attacks. Even without treatment, the paroxysms subside in a few weeks.
A person with P. falciparum malaria, however, is likely to feel miserable even between attacks and, without treatment, may die. One reason P. falciparum malaria is so virulent is that the parasite can infect red blood cells in all stages of development, leading to very high parasite levels in the blood. In contrast, P. vivax parasites infect only young red blood cells, which means the number of parasites in the blood does not reach the same high levels as seen in P. falciparum infection.
Treating Malaria
In most cases, malaria disease can be successfully treated, although the recuperating patient may find it takes several weeks to recover full strength. on the best medicine to use, the doctor should try to identify the species of parasite responsible for the disease and where the patient got the infection. Up-to-date information on the geography of malaria, such as which species are present in which areas, whether chloroquine-resistant parasites are present, and which seasons of the year carry the greatest risk, is available at international travel clinics, CDC, and WHO. In the United States, patients with P. falciparum malaria are usually hospitalized and treated as medical emergencies because their conditions may get worse quickly. Patients should talk with a doctor who specializes in infectious diseases and is knowledgeable about diagnosing and treating malaria and its complications.
Chloroquine, long considered the medicine of choice for treating malaria, is no longer considered the first-line antimalarial drug in many countries, and national malaria control programs are recommending alternatives. chloroquine-resistant parasites are becoming more widespread, doctors must carefully monitor patients who are treated with it.
If the number of parasites in the blood does not drop significantly during treatment, it may mean the parasites are resistant to the medicine. In addition, if a person develops any fever within a period of weeks to months after apparently successful treatment, the medicine may not have gotten rid of all the parasites. Additional treatment may then be required.
Health care workers should watch patients with P. falciparum malaria closely for potentially severe complications, including anemia, kidney failure, fluid imbalance, or respiratory distress. Brain damage can occur following cerebral malaria, which happens when large numbers of red blood cells containing parasites clog tiny blood vessels in the brain.
Preventing Malaria
Before leaving home, anyone traveling to a malarious area should consult CDC, WHO, a knowledgeable health care provider, an international travel clinic, or a local health department to get advice on what medicines to take before, during, and after the trip. Health risks for malaria vary with the destination and types of activities the traveler will undertake.
A traveler who spends even a single night in a malarious area risks getting infected. The first line of defense is to limit contact with mosquitoes by taking these measures.
- Use mosquito repellent
- Keep arms and legs covered
- Stay indoors beginning at dusk and throughout the night (when Anopheles mosquitoes like to feed)
- Sleep under mosquito netting
Credit: National Institute of Health.