Epidemiology

Globally, the overall pooled estimate for Babesia infections in humans is 2.23%, with a continental range of 1.54% in North America to 4.17% in Europe.[9]

Babesiosis has been a nationally notifiable condition in the US since 2011, although it may not be a reportable condition in every state. The incidence increased significantly between 2011 and 2019 in northeastern states. A total of 16,456 cases were reported by 37 states during this time. The states with the largest number of cases were New York, Massachusetts, and Connecticut. Cases increased significantly in Maine, New Hampshire, and Vermont, states not considered to have endemic babesiosis.[10]​ In 2022, 1708 cases were reported, with the majority reported from states in the northeastern and upper midwestern US (i.e., Massachusetts, New Jersey, New York [excluding New York City], and Maine).[11]​ Peak transmission occurs from May to September in upper midwestern and northeastern US.[6]​ In the US, most cases of babesiosis are caused by Babesia microti.[1] However, babesiosis due to species other than B microti (such as B duncani/MO-1) has been reported in northern California, Washington State, Kentucky, and Missouri in the US, and in Canada.[4] CDC: Babesiosis - national surveillance Opens in new window

Babesiosis is rare in Europe, occurring mostly in splenectomised patients in France and the UK, and is most frequently due to B divergens.[8] A case of babesiosis was reported in the UK in 2020.[12] Babesiosis is also rare in other countries. Infection with B venatorum has been reported in East Asia.[13]

Use of this content is subject to our disclaimer