What is babesiosis?

Babesiosis is caused by microscopic parasites that infect red blood cells. Babesia microtis is the main species that has been found in people in the United States.

How do people get infected with Babesia?

The main route of transmission is through the bite of an infected tick. Babesia microti is spread by Ixodes scapularis ticks, which are commonly called blacklegged ticks or deer ticks. Infected people might not recall a tick bite because the ticks can be very small (about the size of a poppy seed).

Other possible ways of becoming infected with Babesia include receipt of a contaminated blood transfusion (no tests have been licensed yet for donor screening); or transmission from an infected mother to her baby during pregnancy or delivery.

(Click on image for a
larger view)Deer Ticks
Image source: Centers for Disease Control and Prevention

Where would an Illinois resident become infected with this organism?

Tickborne transmission of B. microti primarily occurs in the Northeast and upper Midwest, particularly in parts of New England, New York, New Jersey, Wisconsin and Minnesota. Illinois residents who travel to Wisconsin, for example, and spend time in tick habitat may become infected.

What are the symptoms and signs of Babesia infection?

Many people who are infected with Babesia microti feel fine and do not have any symptoms. Some people develop flu-like symptoms, such as fever, chills, sweats, headache, body aches, loss of appetite, nausea, or fatigue. Because Babesia parasites infect red blood cells, babesiosis can cause hemolytic anemia (from destruction of red blood cells). Babesiosis can be a severe, life-threatening disease, in some people (persons without a spleen or who have weakened immune systems).

How soon after the exposure do symptoms develop?

Symptoms, if any, can start within a week or so. They usually develop within a few weeks or months, sometimes longer.

What should I do if I think I might have babesiosis?

See your health care provider. In symptomatic people, babesiosis usually is diagnosed by examining blood under a microscope and seeing Babesia parasites inside red blood cells. Effective treatments are available, and most people respond well. People who do not have symptoms or signs of babesiosis usually do not need to be treated.

Can babesiosis be prevented?

Yes. People can take steps to prevent babesiosis and other tickborne infections. See the Department's Tick Prevention and Control information on the website.

No vaccine is available to protect people against babesiosis.

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Illinois Department of Public Health
535 West Jefferson Street
Springfield, Illinois 62761
Phone 217-782-4977
Fax 217-782-3987
TTY 800-547-0466
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