Babesiosis is a tick-borne disease caused by the parasite Babesia microti. Babesiosis is rare but can sometimes be severe or fatal. It is transmitted through the bite of an infected blacklegged tick. Most cases of babesiosis occur in the warmer months when ticks are most active.

Babesiosis can also rarely be transmitted through a blood transfusion. In 2018 the FDA approved a test to screen the blood supply for Babesia microti.


Many people infected with babesiosis do not have symptoms. Symptoms can include:

  • Fever
  • Chills
  • Sweats
  • Body aches
  • Headaches
  • Tiredness

Health issues from the infection can include anemia and a low platelet count.

Severe infection is most common in people who:

  • Do not have a spleen
  • Have a weak immune system
  • Have other serious health conditions
  • Are elderly


To prevent babesiosis, be aware of where ticks are present. Blacklegged ticks that carry the parasite have been found in Staten Island and parts of the north Bronx. Other areas outside of NYC include Long Island, upstate NY, northeast states, Minnesota and Wisconsin.

Learn how to prevent ticks and tick bites.


Babesiosis is treated with a course of two medications. People with no signs or symptoms usually do not need to be treated. Speak to your healthcare provider for more information.

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