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Microbes

Author(s): Nancy Moreno, PhD, Barbara Tharp, MS, Deanne Erdmann, MS, Sonia Rahmati Clayton, PhD, and James Denk, MA.

Disease Information: Malaria

What do you know about malaria? In the United States, we don’t hear much about this disease, because it was eradicated (removed completely) from our country in the 1950s

But malaria still is a serious threat in warmer and poorer regions of the world, including India, Africa, Central and South America, and tropical parts of Asia. The World Health Organization reports that each year, 300–500 million new cases of malaria are diagnosed, and more than one million people—mostly young children—die from it. 

A Microscopic Parasite
Malaria is a life-threatening disease caused by Plasmodium, a parasite in the protozoan group. A parasite is an organism that lives in, with, or on another organism (or host), from which it obtains nutrients and to which it causes harm. The malaria parasite is carried by female Anopheles (ah-NOF-il-eez) mosquitoes. The symptoms of malaria—severe headache, high fever, shaking, vomiting and chills—appear about 9 to 14 days after an infected mosquito bites a human. There are four strains (forms) of malaria. All are very serious, and one strain often is fatal.

Once a person is infected, the parasite attacks and destroys red blood cells. It also blocks blood vessels leading to the brain or other organs. If medicine isn’t obtained, or if that particular strain of malaria is resistant to (not killed by) the medicine, a malaria infection can quickly become deadly. 

The Cycle of Malaria Infection
We know that when a female Anopheles mosquito bites a person who already has malaria, the mosquito takes in malaria parasites and becomes a carrier. When the mosquito bites someone else, it transmits parasites to (infects) that person. But it’s not clear if the parasite kills the mosquito. It is possible that the mosquitoes are not affected by the malaria parasite.

Once the Plasmodium parasite enters a person’s bloodstream, it travels to the liver, where it begins to grow and multiply. During this incubation period, before the parasite has fully developed, the person will not feel ill, and may not even know he or she is infected. When the parasite moves from the liver to the blood stream, the person will begin to feel symptoms. At this point, the disease has developed enough to infect any Anopheles mosquito that may bite this newly infected person, and the cycle of infection continues. 

People also can get malaria from having a blood transfusion or organ transplant, or by sharing used needles. A pregnant mother infected with malaria can give the disease to her child. But malaria cannot spread from casual contact between people. You can’t get it if someone sneezes on you. 

Still a Deadly Disease
During the 20th Century, malaria was eliminated from most parts of the world that are not hot year-round. But it was not wiped out everywhere, and it may be making a comeback. Evidence suggests that Anopheles mosquitoes have become resistant to pesticides that previously killed them. Mean­while, vaccines that once prevented infection, along with the drugs used to treat malaria, are becoming less effective. Some experts think malaria may be moving into new parts of the world, including places where it once had been eliminated. 

Although scientists believe most deaths from malaria are preventable, this disease remains a major global health concern. It also is preventing development in some of the poorest countries in the world. For example, in Africa, on average, a child dies from malaria every 30 seconds. And even if a child survives malaria, he or she often is left with learning problems or brain damage. 

The U.S. is not entirely free from malaria. Approximately 1,200 infections and 13 deaths from malaria are reported here each year, mostly among travelers and immigrants from parts of the world where malaria remains a problem. Further, Anopheles mosquitoes still exist in the U.S., so it is possible for the mosquitoes to reintroduce malaria into the U.S. 


Funded by the following grant(s)

Science Education Partnership Award, NIH

MicroMatters
Grant Number: 5R25RR018605