by EBSCO Medical Review Board


Babesiosis is a parasite infection passed through the bite of a tick. It damages red blood cells and makes it hard for them to carry oxygen to the body.


Babesiosis is caused by a parasite found in some ticks. An infected tick passes the parasite to humans.

The parasite can also be passed through a blood transfusion from an infected donor. This is not common.

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A Tick

Risk Factors

Things that may raise the risk of this infection are:

  • Spending time in places where there are outbreaks:
    • North America: The Northeast, upper Midwest, and northern Pacific Coast
    • Europe: Various countries and the British Isles
    • Asia
    • Africa
    • South America
  • Having a weakened immune system


Some people will not have symptoms. Others may not have them until a few days or weeks after the bite. They are often flu-like symptoms such as:

  • Fever
  • Chills
  • Sweating
  • Headache
  • Muscle and joint aches
  • Lack of hunger
  • Nausea and vomiting
  • Fatigue
  • Cough

A severe infection can be deadly. It can make it hard to breathe and lead to problems with the heart, liver, or kidney.


You will be asked about your symptoms and health history. You may be asked if you have spent time in places where there are ticks. A physical exam will be done.

Blood tests will be done to look for signs of the infection.


A person without symptoms may not need to be treated. The immune system will clear the parasite from the body.

An infection that causes symptoms will need to be treated with antibiotics and antiparasitic medicines.


To lower the chance of this infection:

  • Avoid tick-infested areas, especially during May to October.
  • Wear light-colored clothing to better locate a crawling tick.
  • Tuck pants into socks when in tick-infested habitats.
  • Regularly inspect and remove ticks from the body when in tick-infested habitats.
  • Remove ticks using fine-tipped tweezers by grasping the tick close to the skin’s surface and pulling upward steadily.
  • Disinfect tick bites with soap and water.
  • Use tick repellents.


Centers for Disease Control and Prevention 

Family Doctor—American Academy of Family Physicians 


Healthy Canadians 

Public Health Agency of Canada 


Babesiosis. Centers for Disease Control and Prevention website. Available at: Updated April 11, 2018. Accessed November 20, 2019.

Babesiosis. EBSCO DynaMed website. Available at: . Updated July 9, 2018. Accessed November 20, 2019.

Vannier E, Krause PJ. Human babesiosis. N Engl J Med. 2012 Jun 21;366(25):2397-407.

Revision Information

  • Reviewer: EBSCO Medical Review Board James P. Cornell, MD
  • Review Date: 09/2019
  • Update Date: 05/27/2020