Babesiosis in Vermont is caused by an infection with a microscopic blood parasite called Babesia microti. These parasites can be transmitted to humans by the bite of infected blacklegged ticks (Ixodes scapularis), the same tick that transmits Lyme disease and anaplasmosis. Babesiosis can also be transmitted by blood transfusion and rarely by congenital transmission, from an infected mother to her baby (during pregnancy or delivery).


Many people who have been infected with Babesia do not experience any symptoms.

When symptoms do occur, they typically begin one to four weeks after a tick bite and can include fever, chills, sweats, headache, body aches, loss of appetite, nausea, or fatigue. Babesiosis can also cause a type of anemia, which makes a person develop jaundice (yellowing of the skin) and dark urine.

Anyone can get sick with babesiosis, but people who have compromised immune systems, kidney or liver disease, those who do not have a spleen, and older adults are at greater risk for serious complications, including death.                

Babesiosis can be diagnosed using blood tests. The disease can be successfully treated with the appropriate medical care.

Who is at Risk in Vermont?

Anyone can get babesiosis, however, 70% of cases reported to the Health Department are in Vermonters 55 years of age or older. Most cases have occurred in residents of the state’s southern-most counties: Bennington, Rutland, Windsor and Windham.

Percentage of Babesiosis Cases by Sex and Age Group Graph
Babesiosis Incidence Map

Trends over Time

Babesiosis is the third most common tickborne disease in Vermont. Yearly reported cases of babesiosis in Vermont increased from two cases in 2011 (incidence = 0.3 per 100,000 population) to 34 cases in 2019 (5.4 per 100,000 population), a 1,602% increase in incidence.

Reported Cases of Babesiosis Graph

When are Vermonters at Risk?

People may be at risk for babesiosis whenever blacklegged ticks are active, but most cases are reported in June through August.

Babesiosis Cases by Month of Illness Onset Graph

Preventing Babesiosis 

The best way to prevent babesiosis is to prevent tick bites.

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