More Health:

March 17, 2023

Deer ticks are fueling the rise of a flu-like illness that isn't Lyme disease

Cases of babesiosis – a once rare illness – have risen by 40% in New Jersey over the last decade, the CDC said. And the disease could become endemic in Pennsylvania

Illness Ticks
Deer Tick Babesiosis Erik Karits/

Blacklegged ticks, commonly known as deer ticks, are known for spreading Lyme disease. But they also are responsible for a rise in babesiosis cases, the CDC says. The illness is now considered endemic in seven states, including New Jersey.

Much of the focus on preventing tick-borne illnesses in the United States has been targeted toward education about Lyme disease, the most prevalent illness associated with bites from blacklegged ticks, or deer ticks.

But over the last decade, cases of a flu-like illness called babesiosis, also transmitted by deer ticks, have more than doubled in some Northeastern states, the U.S. Centers for Disease Control & Prevented reported Thursday.

The infection, caused by microscopic Babesia parasites, primarily is transmitted by tick bites, although people who get blood transfusions and organ transplants also may become ill. In some cases, mothers can transmit babesiosis to their infants.

Some people who become infected with babesiosis may not develop symptoms, but others can experience mild to severe illnesses. Symptoms include high fever, excessive sweating, chills, headaches, muscle and joint pain, and loss of appetite.

The CDC's latest data on babesiosis comes against the backdrop of a general increase in all tick-borne diseases, which climbed 25% in the United States from 40,795 reported cases in 2011 to 50,856 in 2019. What stands out about babesiosis is that its prevalence has rapidly grown in the Northeast.

Although the first case of babesiosis was documented in Massachusetts in 1969, the infection didn't become nationally reportable until 2011. It's now monitored and tracked in 41 states, including New Jersey, where cases increased by 40% from 2011 to 2019. 

In Pennsylvania, which has the highest number of Lyme disease cases in the U.S., babesiosis is not currently a reportable illness. But research that follows how and where infections occurred suggests babesiosis is an emerging illness that could become endemic in Pennsylvania. It's already endemic in New Jersey, New York and five other states, the CDC said. 

The CDC suggested Pennsylvania consider making babesiosis reportable to better identify where the Babesio parasite has become more common. The state Department of Health did not immediately respond when asked whether that is a possibility.

Babesiosis cases spread north

Some states in the Northeast have seen even more dramatic growth in babesiosis cases. Maine, Vermont and New Hampshire — where the parasite previously was not considered endemic — each saw cases jump from fewer than 15 in 2011 to dozens by 2019. The Babesio parasite also is found in the upper Midwest, including Minnesota and Wisconsin.

Once considered rare in the U.S., babesiosis is now prompting the CDC to urge greater awareness and education for people who live in or travel to states where the infection has become prevalent. The majority of cases are reported during the spring and summer months, when tick activity is at its highest.

The CDC believes babesiosis may be spreading north as a result of rising temperatures and growing deer populations.

Although deaths from babesiosis are uncommon, the CDC reported that 957 people were hospitalized with the infection for at least one day in 2019 — about 44% of cases the agency was able to track that year.

The most frequently reported symptom is fever, which occurred in about 78% of cases followed by the CDC in 2019. Muscle aches, chills, headache, low red blood cell count and anemia also were present in more than 50% of cases.

Babesiosis can be especially dangerous to older people and those with weakened immune systems due to cancer, lymphoma or AIDS. People with liver or kidney disease and those who have had their spleens removed also are at higher risk for serious infections.

In Pennsylvania, several cases in older adults in recent years were resolved using antibiotic treatment. In at least one case, a course of the antibiotic doxycycline, commonly used to treat Lyme disease, failed to improve the patient's condition. The preferred medications for severe cases of babesiosis are clindamycin and quinine, the CDC said. Patients with presumptive cases of Lyme disease also may need to be evaluated for babesiosis, which can produce rashes that are distinguishable from Lyme disease.

How to prevent tick bites

With tick season approaching, the Pennsylvania Department of Conservation and Natural Resources advises the public to take the following precautions to prevent tick bites:

• Apply tick repellents containing permethrin to clothing and EPA-registered insect repellents such as DEET to exposed skin before entering the outdoors. Reapply as needed according to product label instructions.
• Wear light-colored outer clothing and tuck shirts into pants, and pants into socks.
• Walk in the centers of trails, and avoid wooded and brushy areas with low-growing vegetation and tall grasses that may harbor ticks.
• After returning home, remove all clothing, take a shower, and place clothing into the dryer on high heat to kill any lingering ticks. Examine gear such as backpacks for ticks.
• Conduct a full-body tick check using a hand or full-length mirror, including hidden areas such as the scalp, ears, armpits, belly button, and between the legs.
• Check over any pets exposed to likely tick habitats each time they return indoors.
• If a tick is found attached to your skin, use tweezers to remove it carefully, including the head. Monitor for symptoms and contact your doctor with any questions.

The New Jersey Department of Health also has a frequently asked questions page with information about babesiosis and what to do in case of a tick bite.

Follow us

Health Videos