Babesiosis, 2017

Babesiosis is a malaria-like illness caused by a protozoan parasite, typically Babesia microti, which infects red blood cells. B. microti is transmitted to humans by bites from Ixodes scapularis (the blacklegged tick), the same vector that transmits the agents of Lyme disease, human anaplasmosis, one form of human ehrlichiosis, and a strain of Powassan virus. Babesia parasites can also be transmitted by blood transfusion. Although most people infected with Babesia have asymptomatic infections, people with weak immune systems, other co-morbidities, and the elderly can become seriously ill.

In 2017, 59 confirmed and probable babesiosis cases (1.1 per 100,000 population) were reported, up from the 50 cases in 2016. Despite slight annual fluctuations, case totals since 2009 (range, 31 to 72) have been consistently higher than reported totals from 2000 to 2008 (range, 1 to 29) (Figure 1), and the overall trend is toward increasing numbers. Demographic and case characteristics are similar in recent years. In 2017, 34 (58%) of the cases occurred in males. The median case age was 64 years (range, 7 to 94), up from 61 in 2016, and older than the median ages for both anaplasmosis (58 years) and for confirmed cases of Lyme disease (43 years). Onsets of illness peaked in the summer months; 47 (87%) of 54 patients with known onset reported first experiencing symptoms in June, July, or August. Nineteen (32%) cases were hospitalized for their infection in 2017 for a median duration of 6 days (range, 2 to 14 days). Although severe complications like organ failure were reported in 7 cases, there were no deaths attributable to babesiosis in 2017.

• For up to date information see>> Babesiosis (Babesia microti)
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2017