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What is Babesiosis?

Babesiosis is caused by microscopic parasites that infect red blood cells. Babesia microti 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.

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. Learn more about Tick Prevention and Control information.

No vaccine is available to protect people against babesiosis.