It's a common ritual of summer: with the warm weather comes more outdoor activities, and more encounters with disease-spreading pathogens. A summer favorite? In the U.S., the Lyme disease-carrying blacklegged tick. And with a new batch of celebrities reporting infections this summer—model Bella Hadid, singer Shania Twain, and actress Riley Keough—it’s worth taking stock of what we know about how prevalent Lyme disease really is, and the best way to protect ourselves from the tiny ticks that spread it.
In 1988, the U.S. Centers for Disease Control and Prevention (CDC) estimated that there were about 400,000 cases of Lyme disease in the country; by 2018, that number had increased to nearly half a million. The actual number of reported cases to the national public health agency, however, has remained far lower, ranging from a few thousand in 1988 to about 400,000 in 2018. It’s not clear yet what is driving the increase in estimated cases, but factors such as climate change, which influences the range of the tick’s habitat, and the steady push of human development into the suburbs, where ticks and small mammals like mice and chipmunks live—as well as the natural hosts for the Lyme bacteria—could also mean more infections in coming years.
Is there a test for Lyme disease?
Yes, although there have been questions about its accuracy. That uncertainty, however, has less to do with the nature of the test itself than with how it’s used, says Dr. Eugene Shapiro, professor of pediatrics and epidemiology at the Yale School of Medicine. Unlike with the COVID-19 test, which detects signs of the SARS-CoV-2 virus responsible for the infection, Lyme disease tests pick up the immune system’s response, in the form of antibodies to the pathogen in question, the bacterium Borrelia burgdorferi. It may take as many as four to six weeks for these antibodies to appear, however, so people may be infected but still test negative for Lyme during that time. That also means that long after the bacteria are gone, the body may still retain these antibodies, and people could still test positive even if they are no longer infected. “The antibody test just tells you that you have been exposed,” Shapiro says. “The Lyme disease test is not a screening test… It’s meant for people who have some probability of having the disease.”
If the test is used among people who haven’t likely been exposed to the bacteria, such as those who live in states where ticks are not endemic (like those in the Southwest), then it might still generate false positive results, since people can produce similar antibodies that were not triggered by the presence of the Lyme bacteria but by other pathogens.
It’s also worth remembering that not all ticks carry the Lyme disease bacteria, and not all ticks that carry the bacteria transmit it when they bite. Depending on the region, anywhere from 30% to 50% of ticks carry the bacteria in their gut, and they need to feed on a person’s blood for 36 to 48 hours in order to transmit the bacteria. For that reason, says Shapiro, even if someone has been bitten by a tick, that doesn’t mean they need to get tested for Lyme. If they develop symptoms such as the hallmark bullseye rash, fatigue, swollen knees, and sudden weakness in facial muscles, then that might justify getting tested. Even then, says Shapiro, doctors may decide a test isn’t necessary since it takes so long for the antibodies to develop and the rash is a pretty reliable indicator of Lyme.
If doctors order a Lyme disease test, the CDC recommends a two-step lab blood test that looks for antibodies the body makes against the Lyme bacterium. Both tests, which work at different levels of specificity for bacterial proteins, need to be positive for a positive Lyme disease test result. The combined tests are relatively reliable in diagnosing Lyme, if performed at the right time, according to the CDC.
Which bacteria cause Lyme?
In the U.S., the majority of cases are caused by Borrelia burgdorferi bacteria. But a recent paper from researchers at Yale University showed that another Borrelia species, Borrelia miyamotoi, first discovered in Japan, could also be causing recurring fevers, meninigitis, and Lyme-like illnesses in the Northeastern U.S. In testing for the prevalence of different Borrelia species in five states in New England, Dr. Peter Krause, from the department of epidemiology of microbial diseases at Yale School of Medicine, and his colleagues found that while B. burgdorferi was the most common, about 2% to 3% of the samples contained B. miyamotoi. “At the present time, B. miyamotoi is not completely unimportant,” Krause says. “It can cause meningitis and other complications that we may not be aware of yet."
Is the CDC’s Lyme disease case tracker accurate?
Because diagnosing Lyme can get a little complicated, CDC’s case numbers show a large difference between reported and confirmed cases of the disease and the CDC’s estimated number of cases. Many people never get tested since they may not see the trademark rash and attribute the other general symptoms of fatigue and achiness to other causes.
What is the best treatment for Lyme disease?
Antibiotics can help the immune system fight off the infection, and most people take them for two to four weeks. The sooner treatment starts, the greater the chances of a full recovery.
Some people who continue to experience symptoms such as fatigue and fever may need to take antibiotics for longer periods of time, and a small proportion of people continue to experience symptoms, including fatigue and foggy thinking, for months or even years after finishing the antibiotic treatment.
Doctors still don’t know what makes people more likely to have this chronic form of Lyme, and are actively investigating why and how more lingering cases occur.
Can you be cured of Lyme?
That depends on how you define “cure.” Since some people will continue to produce antibodies to the bacterium for weeks or even months, they technically will continue to test positive for the disease, even if they no longer have an active infection or symptoms. And still others will continue to have lingering symptoms long after they stop producing antibodies. Generally, however, treating Lyme early with antibiotics can successfully clear the infection for most people.
If I have antibodies, does that protect me from getting Lyme disease again?
That depends on how quickly you are treated after getting infected. “The people who develop early Lyme and are treated early can definitely get infected again,” says Shapiro, since “many of them never develop antibodies.” But those who develop symptoms such as facial palsy, swollen joints, or arthritis as a result of longer term infections may produce enough immunity to protect to some extent against additional infections.
Is there a vaccine for Lyme?
There was a vaccine, LYMErix, approved by the U.S. Food and Drug Administration in 1998, that reduced new infections in immunized adults by 80%. But it was pulled off the market by its manufacturer at the time, SmithKline Beecham (now GlaxoSmithKline), in 2002 after recipients complained of worsening Lyme symptoms after getting immunized and then infected, which led to low uptake of the vaccine.
LYMErix worked in a unique way, by exploiting the bacteria-fighting factory that is the human immune system. Vaccinated people generated antibodies against the bacteria, which live in an infected tick’s gut. Once the tick feeds off the antibody-laden blood of a vaccinated person, those antibodies then traveled into the tick to kill off the bacteria—essentially immunizing the tick against the bacteria it carried.
Recent efforts to create a Lyme vaccine are building on that idea. A new candidate, developed by Valneva and Pfizer, is currently in late-stage human testing, which avoids some of the purported side effects of the original. Researchers are also testing an antibody-based treatment that people can take prior to getting exposed to protect themselves from infection.
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