The bacterial infection is transmitted by ticks, but not every tick bite will make you sick.

By Amanda MacMillan
April 01, 2019

Now that winter has transitioned to spring and temperatures are warming up in much of the country, you’re likely to start hearing a lot about Lyme disease. Rates of this tick-borne illness have been rising steadily in the United States over the last two decades, with most infections happening in April through October.

According to the U.S. Centers for Disease Control and Prevention (CDC), approximately 30,000 cases of Lyme disease are reported each year. But that number only includes cases that are diagnosed and confirmed by doctors, and recent estimates suggest that more like 300,000 people might actually get sick from Lyme disease each year.

There is also a lot of misinformation out there about Lyme disease—including how people actually get it in the first place. Health spoke with Daniel Kuritzkes, MD, chief of the Division of Infectious Diseases at Brigham and Women’s Hospital in Boston, about what to watch out for and how to protect yourself.

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How do you get Lyme disease?

There is actually only one underlying cause of Lyme disease: an infection caused by the bacterium Borrelia burgdorferi. This bacterium is spread through the bites of infected ticks, including the deer tick (also known as the blacklegged tick) and the western blacklegged tick.

“Lyme disease transmission happens when an infected tick bites you and remains attached for long enough to have a blood meal and become fully engorged,” says Dr. Kuritzkes. According to the CDC, ticks usually must be attached for 36 to 48 hours or more before Lyme disease bacteria can be transmitted to their host.

“In the process of sucking the blood from the person, it’s also releasing the bacteria from its salivary glands into the person’s body,” says Dr. Kuritzkes. “If you can discover and remove the tick earlier, before it’s had a chance to do this for very long, you’re much less likely to be infected.”

If a person is infected with Lyme disease, they may begin to show symptoms between three and 30 days after transmission. They may develop a red, circular rash with a white center that looks like a bull's-eye, although not everyone gets this telltale symptom.

Lyme disease can also cause flu-like symptoms, including a low-grade fever, chills, and muscle aches. A blood test can diagnose Lyme disease, and most people feel better after a 10- to 21-day course of antibiotics. (If Lyme disease goes untreated for months or years, it can cause more serious complications, and a longer course of antibiotics may be needed.)

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Can you get Lyme disease from other people or animals?

There’s no evidence that Lyme disease can be transmitted sexually or by touching or kissing a person who has it, says Dr. Kuritzkes. One widely reported study from 2014 found that the bacterium that transmits Lyme disease could be present in semen and vaginal secretions, which sparked fears that the disease could be passed between sexual partners. But there’s never been a reported case of sexual transmission, says Dr. Kuritzkes, and most experts don’t believe you can “catch” Lyme disease in this way.

In rare cases, Lyme disease has been transmitted from a pregnant woman to her fetus or placenta. Fortunately, according to the CDC, treating an infected woman with antibiotics seems to protect the fetus from any negative effects. There’s also no evidence that Lyme disease can be passed through breastfeeding.

And while there have been no reports of Lyme disease being transmitted through a blood transfusion, scientists say it could potentially happen—so people who are being treated for Lyme disease should not donate blood.

There’s also no evidence that people can catch Lyme disease from another animal either—not from eating infected animal meat, nor from being bitten or scratched by a pet. “The types of ticks that usually bite dogs—called dog ticks—aren’t the type that carry Lyme disease, so it’s not likely that a tick attached to your dog would then go on to infect you,” says Dr. Kuritzkes. “But it’s worth noting that if you’re outdoors somewhere where your dog is picking up ticks, it’s likely that you could be picking up ticks too.”

Dogs are less likely to be bitten by deer and western blacklegged ticks, although it does happen—so it’s still important to check your pets after time spent outdoors and to remove any ticks you find. (Even though dog ticks don’t carry Lyme disease, they can also carry other illnesses.) You can also talk to your veterinarian about preventive treatments that can reduce the risk of your pets being bitten by ticks or about a vaccine that can protect dogs from the disease.

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How to protect yourself

Ticks are often found in wooded areas with tall grass, so wearing high socks and long pants when you’re spending time in these habitats can offer some protection, says Dr. Kuritzkes. But that’s not foolproof, he admits, and can be uncomfortable on hot summer days.

That’s why checking for ticks after spending time outside is so important, he adds. Ticks can be found anywhere on the body, but they often like to hide in areas like the groin, armpits, and scalp.

Ticks can also be difficult to spot because they are so tiny: Most humans are infected with Lyme disease by immature ticks, called nymphs, which can be less than 2 millimeters in length. (Adult ticks can also carry Lyme disease, but they’re more likely to be found and removed from people’s skin before they’re able to transmit the bacteria.)

Wearing insect repellant with DEET, or treating your clothing with a permethrin spray, can also help keep ticks away. And if you do find a tick that’s attached itself to your skin, remove it as quickly as possible using fine-tipped tweezers. If you suspect that a tick may have been feeding for more than 24 hours, call your doctor: He or she may suggest you take a prophylactic course of antibiotics to ward off infection.

Although Lyme disease is curable, Dr. Kuritzkes says that avoiding infection is the best scenario. That’s why prevention is so important, even if you have had Lyme disease in the past. “You can definitely get Lyme disease again, and we certainly see people with repeat infections” he says. “The antibodies you get from Lyme disease aren’t like those you get from measles, which convey some immunity.”

That’s one reason it’s been difficult for doctors to come up with an effective Lyme disease vaccine for use in humans. “Hopefully someday we will have one,” Dr. Kuritzkes says. “For now, avoiding tick bites—and removing ticks as quickly as possible—is really the best defense.”

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