What Is Malaria?

Malaria is an acute infectious disease, usually transmitted by the bite of an infected mosquito. Single-celled parasites (plasmodia) carried by the mosquito enter the bloodstream and travel to the liver. There they mature and proliferate for several days or weeks and cause no symptoms. Eventually, however, the plasmodia reenter the bloodstream and infect the red blood cells.

After multiplying for two to three days the parasites cause massive destruction of the red cells. This initiates the classic cycle of malaria symptoms that last 12 to 24 hours.

Malaria symptoms begin as a period of uncontrollable shivering and chills, followed by a fever as high as 105°F. Finally, a period of profuse sweating occurs, which helps the body temperature return to normal. The patient is left exhausted but otherwise temporarily free of symptoms.

However, plasmodia released from dying red cells and those continuing to multiply in the liver infect other red cells and cause repeated attacks, usually every two to three days. If untreated, attacks can continue intermittently for years and may be fatal, although the body gradually builds up defenses against the disease.

While malaria is rarely life-threatening, one form of the disease, caused by the parasite Plasmodium falciparum, releases all of the parasites into the bloodstream at once and produces a single severe attack that is sometimes fatal. Falciparum malaria may be complicated by kidney failure or disseminated intravascular coagulation (DIC).

What Causes Malaria?

  • Malaria is caused by single-celled parasites (plasmodia), usually transmitted to their human hosts via the bite of an infected female anopheles mosquito. This disease is most common in tropical areas.
  • Malaria may be spread during a blood transfusion or by sharing needles for intravenous drug use.
  • Pregnant women with malaria can transmit the infection to their unborn children.

Symptoms of Malaria

  • Headache
  • Sudden chills and uncontrollable shivering
  • High fever and excessive sweating
  • Convulsion
  • Nausea and vomiting
  • Diarrhea
  • Muscle aches and pain
  • Profuse perspiration accompanied by a drop in body temperature
  • Jaundice (yellowing of the skin or whites of the eyes)
  • Anemia
  • Blood in stool

Malaria Prevention

  • Before departing for a tropical or subtropical area, see your doctor or, preferably, go to a travel clinic where you can obtain information on the types of malaria (including drug-resistant malaria) presently found in the area of your destination. Recommendations may include taking the antimalarial drug chloroquine before leaving and for at least four weeks after returning. In a growing number of areas, such as Southeast Asia (e.g., Thailand, Cambodia), Colombia and Africa, plasmodia are resistant to chloroquine. For trips to such places, other drugs, such as mefloquine or doxycycline are necessary.
  • When in mosquito-infested areas, put mosquito netting over beds, use insect repellents and install window screens. Wear long-sleeve-shirts and long pants if you go out during mosquito-prone hours. Stay indoors between dusk and dawn, the hours when mosquitoes feed.
  • Avoid using perfumes, colognes or aftershave when in malarial areas.

Malaria Diagnosis

  • Patient history and physical examination are needed.
  • Blood smears are examined for parasites.

How Malaria Is Treated

  • Hospitalization is often required. The drug chloroquine is administered to kill parasites in the blood. To kill chloroquine-resistant plasmodia, other drugs, such as quinine or quinidine, are used.
  • For malaria other than that due to P. falciparum (which causes only one attack), an additional drug, primaquine, must be taken for two weeks. This kills parasites in the liver, thereby preventing recurrent attacks.

When to Call a Doctor

  • Contact your doctor before traveling to areas where malaria is prevalent.
  • See a doctor if malaria symptoms develop or recur.

In October 2013, the Centers for Disease Control and Prevention (CDC) reported almost 2,000 cases of malaria in the United States in 2011. According to the CDC, this number is the highest since 1971 and indicates a 14 percent increase from 2010.

Nearly all of these malaria cases were contracted overseas—more than two-thirds in Africa—and transmission peaked in January and again in August. Most cases were acquired in India. In 2010, malaria resulted in about 219 million cases and 660,000 deaths worldwide.


Johns Hopkins Symptoms and Remedies: The Complete Home Medical Reference

Simeon Margolis, M.D., Ph.D., Medical Editor

Prepared by the Editors of The Johns Hopkins Medical Letter: Health After 50

Updated by Remedy Health Media

Publication Review By: the Editorial Staff at Healthcommunities.com

Published: 26 Oct 2011

Last Modified: 10 Mar 2015