Health & Science

Babesiosis Cases Rise in the US. What You Should Know About This Tick-Borne Disease, According to Experts

Cases are increasing in eight states, and the disease is considered endemic in three more states than before, according to a CDC report

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Cases of a worldwide tick-borne disease have significantly increased in the Northeastern United States between 2011 and 2019, according to a new report by the Centers for Disease Control and Prevention.

Babesiosis is caused by microscopic parasites that invade red blood cells. Blacklegged or deer ticks, the same type of tick that transmits Lyme disease, carry the parasites and can send them into people’s bloodstreams after biting them.

Previously, seven states had known endemic transmission: Connecticut, Massachusetts, Minnesota, New Jersey, New York, Rhode Island and Wisconsin.

But the disease is moving northward.

Three states in New England that once had only sporadic incidents of babesiosis — Maine, New Hampshire and Vermont — have been added to the endemic list, meaning there has been a constant amount of the disease present in those states over consecutive years, the agency said.

Although the first case in the U.S. was confirmed on Nantucket Island, Massachusetts, in 1969, the CDC started monitoring babesiosis in 2011 when it became a nationally reportable condition, with thousands of cases in the Northeast and the Midwest.

Nearly 16,500 cases of babesiosis across 37 states were reported from 2011 to 2019, with 98.2% of the cases coming from the 10 aforementioned states, according to the CDC report.

Cases increased in eight states — Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island and Vermont — while cases in Minnesota and Wisconsin remained stable, the agency said.

Dr. Edouard Vannier, a babesiosis expert at Tufts Medical Center, largely attributes the disease stretching to the U.S. border with Canada to global warming.

“As the temperature becomes warmer and the winters are milder, the ticks are surviving better,” Vannier told NBC. “People have to be very careful when they go into any endemic areas where ticks are present.”

Beyond rising temperatures, Dr. Peter Krause, a babesiosis expert at the Yale School of Public Health, points to other reasons for rising cases, such as the aging population, the growing number of people building homes in tick-infested areas, more public awareness and the increase in deer, which are important in the lifecycle of deer ticks.

"Deer can carry hundreds of these ticks on them," Krause told NBC. "Wherever deer are found, the number of ticks is amplified, and you have more of these tick-borne diseases."

While some people with the disease are asymptomatic, many experience flu-like symptoms like fever, chills, sweats, headaches, fatigue, and muscle and joint pain.

Krause said some complications include pulmonary edema (fluid in the lungs), anemia, and heart, lung, kidney or liver failure. Some patients become unaware of their surroundings. Babesiosis can also be fatal; there were eight reported deaths from the disease in 2019.

Both experts consider those who are above the age of 50 to be at higher risk.

“Some of them will be very sick despite having no immune suppression whatsoever,” Vannier said. “As you advance in age within that category, you are at greater risk of severe disease.”

Other people at risk of severe disease include people who are immunocompromised and those who are asplenic, or without a spleen. Krause said the mortality rate in some immunocompromised groups could be as high as 20%.

As for treating mild and severe cases, experts say the first-line regimen is taking a combination of antibiotics, such as azithromycin and atovaquone. Vannier said symptoms typically subside one to two days after starting treatment.

The CDC recommends people living in or traveling to high-incidence states wear long pants and tick repellant, conduct tick checks and avoid underbrush and long grass.

In addition to these protective measures, Vannier said more effort should go toward developing a vaccine.

“There are already efforts toward the development of a vaccine for Lyme disease,” Vannier said. “I think it’s about time that we actually push for a vaccine against babesiosis.”

Individuals not living in tick-infested areas can contract the disease in several ways. One way is through tick transmission, the overwhelming cause of disease transmission, by traveling to endemic areas. Another way is through blood transfusion, but screening blood donors and testing their blood has significantly lowered transmission.

Another species called Babesia duncani has been reported on the West Coast, but the incidence is extremely low, Vannier says.

Despite the lower chances of being infected in non-endemic areas, Vannier and Krause agree on the importance of the general public being aware of the tick-borne disease.

“Physicians think about testing for it, or someone who comes in with a fever may have read about it and says to their physician, ‘I’m wondering about babesiosis,’” Krause said. “That’s why the CDC reporting is so important because it makes healthcare workers and the general public aware of this disease being present in their area.”

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