Lyme disease cases have gone up in the U.S. Here's why — and how to protect yourself.

About 63,000 cases of Lyme disease were reported to the Centers for Disease Control and Prevention in 2022, according to a report released last month. That’s a nearly 70% jump in the number of cases that were reported in 2021. While the number is alarming and appears as though infections are on the rise, the reality is not that simple. Here’s what’s going on: The CDC changed its case definition of Lyme disease in 2021, which resulted in an increase in the number of cases reported through the Nationally Notifiable Diseases Surveillance System (NNDSS), which is its passive reporting system used to collect case data.

However, the CDC notes that, even after that revision, the most recent data likely underrepresents the real number of annual cases because the NNDSS primarily uses positive lab reports to count them, and Lyme disease is often diagnosed and treated without testing. “This is in part due to the need to start treatment right away and not wait for testing, which can be negative early in the disease process,” Dr. Mark Loafman, a family physician with Cook County Health in Illinois, tells Yahoo Life.

A 2021 report that investigated insurance claims from 2010 to 2018 found that an estimated 476,000 patients were diagnosed with and treated for Lyme disease annually — significantly more than the CDC’s previous estimation that around 300,000 Americans get Lyme disease each year. That higher number may be a more accurate national representation, but the CDC says that it’s likely an overestimation because many patients treated for Lyme disease are not actually infected.

Bottom line: There is no way of knowing exactly how many people get Lyme disease each year. But the latest numbers are enough to make anyone worry about contracting it. Here, experts explain what Lyme disease is, which areas are hot spots and what you can do to stay safe.

What is Lyme disease and how is it contracted?

Lyme disease is an infection caused by spiral-shaped bacteria known as spirochete, the most common ones in the U.S. being Borrelia burgdorferi and Borrelia mayonii, Dr. Bobbi Pritt, a Mayo Clinic microbiologist, pathologist and Lyme disease expert, tells Yahoo Life. “Most people get it after being bitten by an infected black-legged tick, also called a deer tick,” Pritt adds. “These ticks become infected with the Lyme bacterium by biting an infected rodent, bird or other animal.”

Symptoms can show up within three to 30 days after a tick bite. Most people develop a target-shaped rash at the site of the tick bite and flu-like symptoms including fever, chills, fatigue, headache, lack of appetite, neck stiffness, swollen lymph nodes and muscle and joint pain, explains Pritt. However, some people don’t get a rash at all, “or fail to notice it if it’s on the back, scalp or other hard-to-see area,” she says.

How is Lyme disease treated?

If left untreated, the infection can spread and symptoms may worsen, resulting in arthritis, bone and joint pain, additional rashes, inflammation of the brain and spinal cord and facial palsy (one-sided facial droop), explains Pritt. “Involvement of the nerves can cause shooting pains or numbness in the hands and feet,” she says. Although not common, “involvement of the heart can lead to inflammation and rarely death.”

Treatment for Lyme disease varies depending on the case and symptoms, but almost always includes a course of oral or intravenous antibiotics, per the CDC. Even with treatment, though, 5% to 10% of infected individuals have persistent symptoms including fatigue, body aches and brain fog, Pritt says. “It can take months for these symptoms to go away,” she says. “Therefore, it is important to take steps to prevent Lyme disease whenever possible.”

What are the hot spots for Lyme disease?

Hot spots for Lyme disease are the Northeast, Upper Midwest and West Coast, as evidenced by the CDC’s Lyme disease map. Not surprisingly, vast areas of brush and trees cover these areas, where hiking and outdoor recreation are popular. “In the past, Lyme disease appeared to be limited to specific regions of the U.S.,” says Loafman. But anywhere with dense forestation presents risk.

Climate change could also be making things worse, adds Loafman, as deer ticks thrive in warm environments. Freezing temperatures typically control their population, according to NASA, but as winter temperatures rise in the northern U.S. and Canada, so does Lyme disease risk.

5 ways to protect yourself from Lyme disease

There are steps you can take to lower your risk of tick bites and Lyme disease, according to Loafman and Pritt.

• Avoid hot spots. Using the CDC’s map as a guide, it’s wise to avoid Lyme disease hot spots, especially in warmer months. If that’s not possible, and you spend extensive time outside in those regions, Pritt recommends avoiding dense vegetation like tall grasses and leaf litter, environments in which ticks thrive.

• Wear protective clothing and tick repellent. During outdoor activities, it’s crucial to wear clothing that covers your skin — even when it’s hot. “Tucking your pants into your socks can be an easy and effective way to keep ticks from biting your legs,” Pritt says. She also recommends using tick repellents such as Deet, Picaridin and oil of lemon or eucalyptus. For an added layer of protection, you can treat clothes and gear with the insecticide permethrin.

• Complete thorough tick checks often. Especially after being outdoors, it’s important to scan the entire body for tick bites. Loafman notes that deer ticks are tiny, “so the skin inspection must be thorough and close,” he says. The insects like to burrow snugly against the skin, he adds, which makes the groin, armpits, inner elbows, waist band and sockline common areas for them to hide.

• If you find a tick, remove it immediately. “Ticks take their time setting up shop to feed on your blood, so it generally takes 36 to 48 hours to transmit infection,” says Loafman. That means the sooner you remove a tick, the less likely you are to get sick. Still, Loafman advises doing so carefully and with caution — Pritt suggests using tweezers — because crushing or injuring the tick can cause injection of its saliva and make things worse.

• Save the tick and see your doctor as soon as possible. After tick removal is complete, Loafman recommends putting it in a sealable plastic bag and taking it to your primary care provider, whom you should see as soon as possible. “Depending on the circumstances, they may want to see the tick to help determine the risk,” he says. Most important, if you suspect you were bitten — whether or not you found a tick — it’s important to see a doctor. “Treatment can help even if days or weeks have passed,” Loafman says.