What is babesiosis?

Babesiosis is a rare, sometimes severe or fatal tick-borne disease caused by Babesia microti , a protozoan parasite that infects red blood cells. The disease can cause fever, fatigue, jaundice, and anemia lasting from several days to several months. People who are elderly or immunocompromised (including people without a spleen) are most likely to be infected and most likely to have a severe infection. Many infections can occur without producing symptoms.

Babesiosis in New York City

Babesiosis is transmitted by the bite of an infected blacklegged tick, Ixodes scapularis , the same tick that transmits Lyme disease and anaplasmosis . Ticks become infected by feeding on infected mice or meadow voles. Highly endemic areas for Babesia microti in the greater New York City region include Suffolk County (especially Fire Island and Shelter Island), portions of Connecticut and New Jersey, and Nantucket Island off the Massachusetts shore. Transmission risk is greatest during the spring and summer. For more information about the blacklegged tick, visit the tick page.

For more information on the number of NYC residents reported with babesiosis, please visit EpiQuery.

Can babesia be transmitted through blood transfusion?

Yes. Although rare, there have been several reports of transfusion-transmitted babesiosis. Persons infected with babesia may not show signs of illness. If a person with babesiosis donates blood, the infected red blood can then cause infection in the person who receives the blood products. At this time there is no babesia testing done on donated blood.

How can babesiosis be prevented?

For more information on ticks and preventing tick bites, including the use of repellents go to ticks and tick prevention.

How should a tick be removed?

For guidance on the appropriate way to remove a tick, please go to ticks and tick prevention.

For more information

For more information, please visit CDC's babesiosis web page.

Information for professionals

For more clinical, diagnostic, and treatment information please see Zoonotic & Vectorborne Disease Provider Information.