Why confirmed cases of Lyme disease have increased


Recent tracking rule changes have led to a significant increase in reported Lyme disease cases in the United States.

The Council of State and Territorial Epidemiologists and the Centers for Disease Control and Prevention updated definitions to better understand the tick-borne disease. In 2022, reported cases rose by 68.5 percent after the new definition went into effect.

“The new Lyme disease case definition allows us to get a more accurate count of Lyme disease cases in high-incidence areas, which will improve our understanding of Lyme disease and its impact on people living in the United States,” said Dr. Bobbi Pritt, director of the Clinical Parasitology Laboratory at Mayo Clinic.

Lyme disease is a bacterial infection caused by the bite of an infected black-legged tick, commonly known as a deer tick. It is most common in the Upper Midwest and the Northeast and mid-Atlantic states. And it’s also common in Europe, Asia and in south-central and southeastern Canada.

Patients may present with a rash at the site of the tick bite — classically with a bull’s-eye rash. But that’s not always the case.

“Also, some people may have a rash and not know if it’s on the back of their head or another hard-to-see and hard-to-reach area,” Pritt said. “If the infection is not treated right away, the patient may then progress to having other symptoms, like disseminated rashes, joint pain, arthritis and even neurologic involvement. And they can even have one-sided facial paralysis, called Bell’s palsy.”

Lab tests help confirm or rule out diagnoses of Lyme disease. Pritt says that Mayo Clinic Laboratories perform more than 300,000 tests for tick-borne diseases each year.

The best way to avoid infection is to avoid getting a tick bite. Pritt said it’s important for people to protect themselves from tick bites. Avoiding tick bites will protect them not just from Lyme disease, but also many other tick-borne infections.

Some tick bite prevention tips include:

  • Avoiding areas where ticks are frequently found.
  • Using a repellent with 30 percent or more of DEET.
  • Wearing clothing that covers your arms and legs.
  • Tucking  pants into socks while hiking.

“I also like oil of lemon eucalyptus, shown by the Environmental Protection Agency to be almost as effective as DEET, and smells a little better,” Pritt said. “Also, wearing permethrin sprayed on clothing is helpful. That also will repel and even kill ticks. Then, just cover up with clothing so that the ticks can’t get to your skin. If you tuck your pants into your socks, you’re taking away an avenue for ticks to get to your legs to bite you.”


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