Rates of This Tickborne Disease Are on the Rise—Here Are the Symptoms to Look For

Researchers at Penn State analyzed a large database of clinical patient data that included over 250 million people and found that the rate of babesiosis infection rose 9 percent per year on average from 2015 to 2022.

Here’s more on the disease and how to avoid it.

What is babesiosis?

Babesiosis, sometimes referred to as “American malaria,” is a disease caused by the Babesia parasite that’s spread primarily through tick bites—typically via blacklegged or deer ticks, according to the Centers for Disease Control and Prevention (CDC). The parasite infects the host’s red blood cells.

Babesiosis is sometimes found alongside other diseases; the study says 4 in 10 people with the disease were co-infected with another tickborne illness. But interestingly, having both babesiosis and Lyme disease isn’t associated with a higher mortality risk, the researchers say. In fact, it’s the opposite: The mortality risk is higher for people who have babesiosis alone.

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Babesiosis is on the rise

Babesiosis isn’t as common as Lyme, but it is on the rise. “We found a 9-percent-per-year increase in babesiosis cases in the U.S., although it could be higher,” Paddy Ssentongo, MD, PhD, a physician-scientist and the lead author of the study, tells Well+Good.

He believes several factors could explain this. The first is climate change, or a warmer climate, which influences the population and distribution of ticks and their hosts, leading to a larger geographic spread. (This may also explain why cases peak during the summer.)

Second, human behavior. “Encroachment of the wooded/forested regions home to the reservoir host for Babesia infection has increased the interface between the reservoir host and humans,” he says. (In other words, people are spreading into tick territory more and more, which increases the number of bites.)

Third, there’s just more awareness around Babesia and clinical manifestations, so more healthcare providers are able to give this accurate diagnosis, Dr. Ssentongo says.

The symptoms of babesiosis

Signs of babesiosis don’t start until one to four weeks after exposure, according to the Cleveland Clinic, and about a quarter of infected people have no symptoms at all. When symptoms are present, they include high fever, tiredness, chills, sweating, headache, muscle or joint aches, loss of appetite, and cough.

Because many other diseases share these symptoms, it’s important to ensure you get the right testing done at the doctor’s office. (Babesiosis is diagnosed via a blood test.)

Seeing a medical professional is especially urgent if you show symptoms of severe babesiosis. These include yellowish skin or eyes, pale skin, dark pee, shortness of breath, nausea and vomiting, abdominal pain, neck stiffness, and sudden mood changes or extreme emotional reactions.

How it’s treated

Babesiosis can be treated, according to the CDC, though most asymptomatic people don’t require treatment.

For most people who do have symptoms, a seven- to 10-day course of two prescription medications is the go-to. Usually, the medications are atovaquone (an anti-parasite) and azithromycin (a type of antibiotic). Folks who are immunocompromised may need a longer course of treatment.

Dr. Ssentongo says doxycycline, another type of antibiotic, may also be added to the treatment plan.

Your best bet, though? Prevention.

Should we be worried about babesiosis?

People with certain health risks or careers may want to be extra cautious about this disease. Dr. Ssentongo says anyone can be infected, but people without a spleen, folks who have weakened immune systems (like those with cancer or HIV), and people older than 50 are at an increased risk for complications.

As far as careers, it’s really about how often you’re outside. Preventing tick bites is especially important for folks who are outdoors for long hours. Dr. Ssentongo recommends using tick repellents, wearing long pants, and avoiding long grass. If you find a tick attached to your body, he says, send it for tickborne disease testing and get yourself evaluated by a healthcare provider.

It’s also important to note that babesiosis is endemic to certain U.S. states: Connecticut, Massachusetts, Minnesota, New Jersey, New York, Rhode Island, Wisconsin, Maine, New Hampshire, and Vermont. The spread has extended to Pennsylvania, too, according to Dr. Ssentongo.

If you live in one of those areas, you may want to be extra mindful of any symptoms that arise.

“This epidemiologic shift of infection should create awareness to be placed on prevention strategies for prevention of tick bites,” Dr. Ssentongo says, “but also to produce heightened vigilance among healthcare providers to diagnose and treat Babesia cases early.”