Lyme is not the only disease to worry about this tick season. What you need to know this spring.

Cases of babesiosis — a tick-borne disease that can cause flulike symptoms — are on the rise in the Northeast, according to the CDC.

A black-legged tick waving its front legs at the tip of a blade of vegetation.
The black-legged tick, otherwise known as the deer tick, can spread Lyme disease and babesiosis. (Reuters)

Spring is in full swing, and that means more sunlight, warmer temperatures and more time spent outdoors. It also means that for most of the United States, tick season has begun. Although tick exposure can occur year round, these insects are most active during the warmer months, starting in April.

Some states with greater tick activity have started to urge citizens to take precautions when enjoying the outdoors. Ticks carry several types of disease — Lyme disease being the most common — but health experts say Americans should be aware of a rise in other tick-borne illnesses in some regions of the country, including babesiosis.

What is babesiosis?

Babesiosis is a tick-borne disease caused by a parasite called Babesia microti and spread by the black-legged tick, otherwise known as the deer tick. In the U.S., the disease is more commonly found in the Northeast and Midwest, where deer ticks are abundant.

A bite from a tick carrying this parasite can infect red blood cells. While not everyone who is infected develops symptoms, some people can experience flulike symptoms such as fever, chills, muscle pain and fatigue.

Severe cases of babesiosis are rare, but the disease can be fatal for some people, particularly those who are immunocompromised, according to the Centers for Disease Control and Prevention. The agency also notes that the disease can lead to health complications, including acute respiratory distress and kidney failure.

Cases of babesiosis are increasing in the Northeast

This month, the CDC warned about a significant increase in tick-borne illnesses in the U.S. A study conducted by the agency found that U.S. tick-borne disease cases had risen by 25%, from 40,795 cases reported in 2011 to 50,856 in 2019. During the same period, "a total of 16,456 cases of babesiosis were reported to CDC by 37 states, including 16,174 (98.2%) reported from the 10 states included in this analysis," the report noted.

Cases of babesiosis in particular climbed significantly in eight Northeastern states: Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island and Vermont.

Three New England states — Maine, New Hampshire and Vermont — saw the fastest growth in cases, which prompted the CDC to add them to the list of places where the disease is considered endemic (meaning it is consistently present).

“It's certainly something that is of concern,” Griffin Dill, tick lab coordinator at the University of Maine Cooperative Extension, told Yahoo News. “It hasn't reached the kind of case numbers that we're seeing with Lyme disease or anaplasmosis quite yet, but it is certainly on the rise and something to be aware of.”

Although babesiosis cases are increasing, Lyme disease continues to be the most commonly reported tick-borne disease in the U.S., with approximately 35,000 cases reported to the CDC each year.

Dill and his team provide tick identification and testing services in Maine. By testing ticks that people bring to the lab, his team can identify the type of pathogens the insects could be carrying. Dill explained that this tool is an important one because it provides people with “a piece of risk information about the ticks on their property.” It also gives researchers a better understanding of the geographical spread of ticks and the diseases they carry.

The recent CDC report, Dill said, confirms what he’s been seeing in his lab.

“Just over the past five years that we've been doing this, we've seen an increase over time in the infection rate for Babesia,” he said. “So even just in a relatively short, five-year time frame, we're seeing increases in the parasite within the tick itself, which then can correspond to increases in human cases as well.”

Experts believe that the actual number of cases is probably higher, because babesiosis is not reportable in all states. A main concern about the increased prevalence of the disease is that the parasite that causes it can be transmitted via blood transfusions. This, the CDC said, could pose a threat to the blood supply.

“Persons who acquire babesiosis through contaminated blood have been shown to have significantly worse health outcomes and a higher risk for death than do those who acquire the disease from a tick bite,” the agency said in the report.

However, government health agencies have already taken steps to protect the blood supply from the tick-borne disease. Since 2019, the Food and Drug Administration has recommended screening for the parasite at blood donation centers in 14 states and Washington, D.C., where the disease is more prevalent.

A collection of purple cells, one enlarged with a much darker purple blotch.
Blood sample showing the Babesia parasite. (Smith Collection/Gado/Getty Images)

Why are tick-borne diseases on the rise?

The CDC hasn’t explained why cases of babesiosis and other tick-borne diseases are up, but tick experts have a few theories as to why this may be happening.

Researchers say global warming is a contributing factor. Ticks thrive in warm and humid weather, usually anywhere there is lush greenery. As winters get warmer and shorter, the pests can stay active year round, causing more infections.

Dill said that seasonality patterns of black-legged ticks have almost disappeared.

“Normally, we get kind of a break in tick activity during the winter months, when it's cold, it's snowy, but with warmer weather [and] warmer temperatures, we can and do see them active year round, unfortunately,” he said.

The changes in climate and weather patterns have also had an impact on the geographic range of ticks. The habitat of black-legged ticks and other tick species is expanding, Dill explained.

“The black-legged tick, we're certainly seeing them advance further and further north into northern New England and into Canada,” he said.

Another type of tick that has been on the move in the past two decades is the lone star tick. These ticks can spread an unusual disease called alpha-gal syndrome, which causes an allergic reaction to mammal meats such as beef, pork and lamb. They were historically found in the Southern U.S., but Stephen Rich, director of the New England Center of Excellence in Vector-Borne Diseases, said they are moving north, and farther inland. Their population is also growing.

“There are spots like Long Island, N.Y., where basically the lone star ticks have almost replaced the ticks that transmit Lyme disease — the black-legged ticks. So they're definitely moving northward,” he said.

Both Dill and Rich said climate change is not the only reason why ticks and tick-borne diseases have spread throughout the country.

“We can't say that it's not global warming. But the stronger evidence is that this has to do with the way we manage our landscapes,” Rich said.

The way we like to see our properties, with stone walls and lawns with wooded edges, turns out to be perfect for deer and for deer ticks or black-legged ticks. "We've cultivated landscapes that are perfect for ticks and tick-borne diseases,” he added.

A live specimen of the lone star tick (A. Americanum) in a lab in Morrill Hall at the University of Illinois at Urbana-Champaign in 2017.
The lone star tick gets its name from the single, silvery-white spot on the female's back. (Brian Cassella/Chicago Tribune/Tribune News Service via Getty Images)

How to prevent tick-borne disease

The best way to protect yourself from babesiosis and other tick-borne illnesses is to avoid getting bitten by a tick.

These critters live in grassy, brushy and wooded areas, so you are more likely to have encounters with them when going outside to garden, walk your dog or go camping or hiking.

To prevent tick bites, Dill recommends that people create a layer of protection.

“That barrier can be something as simple as just wearing protective clothing, so wearing long pants and tucking those pants into your boots or into your socks, just anything that's going to prevent a tick from actually getting to your skin,” he said.

Using repellents is also a good option. Certain repellents are designed to be used on clothing; others can be applied directly to the skin. The CDC recommends using Environmental Protection Agency-registered insect repellents. If you are not sure which product to use, the EPA has a search tool that can help find the best fit for you.

Checking your body for ticks after spending time outdoors is also highly recommended.

“Just make it a routine to look over your body and see if you have ticks,” Rich said, adding that people should check their children and pets as well.

Finally, if you do find a tick on yourself, the experts said there’s no reason to panic, because not every tick is carrying a disease. If the insect has bitten you, the CDC recommends removing it with fine-tipped tweezers and cleaning the bite area with rubbing alcohol or with soap and water.

Rich told Yahoo News that people should also consider saving or photographing the tick so a professional can evaluate it and determine if it is carrying harmful bacteria. He recommended the University of Rhode Island’s TickSpotters program, which offers free tick identification service, as one place where this can be done.

If you develop a rash or fever after getting bitten by a tick, the CDC recommends that you consult a medical professional.

“I think awareness is kind of the key there,” Dill said. "We don't want people to be afraid of these illnesses and … prevent people from going outdoors and enjoying outdoor activities. But be aware and take some precautions when recreating outside."