Babesiosis Cases Rising in the Northeast, CDC Reports

The CDC reported that babesiosis cases have been rising in eight states across the United States, and has been declared a new endemic in three more states.

In a report released by the CDC on March 16, the agency reported a tick-borne disease called babesiosis had been declared an endemic in three new states: Maine, New Hampshire, and Vermont. Before the three states, Connecticut, Massachusetts, Minnesota, New Jersey, New York, Rhode Island, and Wisconsin faced heightened babesiosis cases. The report also revealed that from 2011 to 2019, only Minnesota and Wisconsin saw a reduction in cases among the 10 states that dealt with babesiosis.

"Nine years of data show [an] increase in tickborne disease in parts of the U.S. that previously saw few cases," says an epidemiologist with the CDC’s Division of Parasitic Diseases and Malaria Megan Swanson, also the co-author of the report.


Between 2011 and 2019, approximately 16,456 cases of babesiosis were reported to the agency by 37 states, including 16,174 reported from the ten states included in the data.

Babesiosis is a disease caused by microscopic parasites that contaminate our red blood cells and are disseminated by particular ticks. Cases usually culminate in warmer months in the Northeast and upper Midwest. Fortunately, babesiosis can be prevented and often does not require treatment.

Symptoms of babesiosis

In most cases, individuals infected with Babesia microti do not show any symptoms. Certain individuals may present flu-like symptoms, including fever, chills, nausea, and fatigue. Since Babesia parasites contaminate and kill red blood cells, it can often lead to hemolytic anemia, a type of anemia where red blood cells are destroyed faster than their production.

"Sometimes the patient will have felt just fatigued and not quite right, maybe a low-grade temp for a week or two, and then all of a sudden they get worse," shares a senior research scientist at the Yale School of Public Health, Peter Krause, M.D., with NBC News. "That’s usually not the case with Lyme — you get it and then, bingo, you have the rash and so on."

Although babesiosis can be prevented and most people can recover without any treatment, it can be fatal to those without a spleen, who have a weakened immune system, severe health complications, or older. If needed, there are medication options for those with babesia, including atovaquone, azithromycin, clindamycin, and quinine.

Babesia microti is passed on by Ixodes scapularis ticks, often known as deer ticks, which are often found in brushy, woody, and grassy regions in specific areas. Currently, no vaccination is available, so it is essential to stay vigilant while participating in outdoor activities if you reside in certain regions.

To avoid getting infected with Babesia microti, the CDC recommends applying repellents to your skin and clothing when participating in hiking activities. It can also help to wear full-covering clothes, like socks and long pants, to avoid ticks from crawling inside your clothing. After a day of outdoor activities, checking for ticks and removing any if you see them is crucial.


Krause concludes: "It tends to be the more severe cases, the ones that get into the hospital, that are reported. Babesia is much more of a problem than the general public recognizes and can be fatal — up to 20% — in people who have HIV/AIDS or severe cancer with chemotherapy or individuals who lack a spleen."


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