Babesiosis is an infection that damages the red blood cells. Red blood cells travel in the blood and carry oxygen throughout the body. Damage to a large number of these cells can decrease the level of oxygen in the blood.

Mild babesiosis may not cause symptoms. Severe illness can lead to serious and life threatening problems because of the destruction of red blood cells.

Babesiosis is caused by a Babesia parasite. It is most often passed to humans through a bite from an infected tick.

Rarely, the parasite can be passed through a blood transfusion from an infected donor.

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A Tick