Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

Lyme disease is a “tremendous” public health problem, infecting 10 times more Americans than reports have suggested, the Centers for Disease Control and Prevention reports.



New estimates suggest that 300,000 people are infected with the tickborne illness every year.

“This new preliminary estimate confirms that Lyme disease is a tremendous public health problem in the United States, and clearly highlights the urgent need for prevention,” says Dr. Paul Mead, chief of epidemiology and surveillance for CDC’s Lyme disease program, based in Ft Collins, Colo.

“We know that routine surveillance only gives us part of the picture, and that the true number of illnesses is much greater,” Mead added in a statement.

Lyme disease is caused by bacteria called Borrelia burgdorferi, carried by blacklegged ticks. Infection causes fever, headache, fatigue, and a characteristic skin rash called erythema migrans. The infection can spread to joints, the heart, and the nervous system if it’s not treated.

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

More than 300,000 cases of Lyme disease are reported to CDC every year, making it the most commonly reported tick-borne illness in the United States, the CDC says. But some reports have suggested it is far more common than that.

Mead and colleagues looked at several sources, including medical billing records of 22 million people, a 2008 survey of laboratories processing blood tests and a survey of patients asking if they ever had Lyme disease. Taken together, the data indicate that 300,000 Americans are diagnosed with Lyme disease every year, Mead’s team told the International Conference on Lyme Borreliosis and other Tick Borne Diseases being held in Boston this week.

“Not everyone diagnosed or treated for Lyme disease is necessarily infected with Borrelia burgdorferi,” they wrote in a summary submitted to the conference. “Nevertheless, these results are consistent with earlier estimates that Lyme disease cases are underreported by a factor of three- to 12-fold.”

Treatment can be as simple as a single dose of the antibiotic doxycycline or it can involve a three-week to one-month course of antibiotics, depending on how long it takes to diagnose after infection. Infectious disease experts disagree on whether longer courses of treatment are helpful. Up to 20 percent of patients have long-term symptoms, the CDC says.

Lyme disease is most common in the Northeast and Midwest but cases have been reported from all 50 states. It has a complex life cycle involving mice and deer, and it’s usually the small, immature ticks, found on rodents, that are to blame for infecting people.

“That’s why it’s important to carefully check your body and clothing for ticks after being outdoors in woody and grassy areas. If you see a tick, you can lessen the chance of infection by removing it from your body early, even if it’s already begun to feed,” the National Institutes of Health advises.

There used to be a vaccine, but its maker stopped manufacturing it because too few people asked for it. The CDC recommends using an insect repellent that contains DEET, careful checking for ticks after being outdoors, and staying out of bushy, wooded areas.

“We know people can prevent tick bites through steps like using repellents and tick checks. Although these measures are effective, they aren’t fail-proof and people don’t always use them,” the CDC’s Dr. Lyle Petersen said in a statement. “We need to move to a broader approach to tick reduction, involving entire communities, to combat this public health problem.”

This might include killing ticks in back yards, control of rodents that carry the Lyme disease bacteria, and suburban planning involving deer and their interaction with people. Deer carry adult ticks that can carry the disease.