The newest STD: Lyme disease?

An estimated 300,000 Americans are diagnosed each year with Lyme disease, a tick-borne illness that, if untreated, can cause serious health problems, including arthritis, facial paralysis, and even cardiac arrest. The disease is on the rise in some states, particularly in the Northeast, and last year, the Centers for Disease Control and Prevention (CDC) released a report revealing that 10 times more Americans have contracted the disease than previously estimated.

And now an international team of researchers has published a small study with a controversial new theory explaining why: Lyme disease may be sexually transmitted.

"Our findings will change the way Lyme disease is viewed by doctors and patients," said Marianne Middelveen, a microbiologist from Canada and the lead author of the study, which was published this month in the Journal of Investigative Medicine. "It explains why the disease is more common than one would think if only ticks were involved in transmission."

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The research team, which includes two molecular biologists from the United States, tested semen and vaginal samples from three groups of subjects: A control group without the disease, a group of individuals who had tested positive for the disease, and a group of heterosexual married couples who both had the disease, and who were having unprotected sex. The semen and vaginal samples of several participants tested positive for the bacteria that causes Lyme disease. The researchers also found one married couple had identical strains of Lyme bacteria in their samples. Experts note that it's extremely unlikely that one tick would be able to infect two people, given the insect's life cycle.

For now, the CDC reports that "there is no credible scientific evidence that Lyme disease can be spread from person-to-person through sexual contact." The CDC says that even though Lyme bacteria resembles syphilis, the tick-borne disease cannot survive on the surface of skin or in genital secretions. The agency also notes that it is not uncommon for more than one person in a household to develop the disease, since they tend to share an environment where ticks may be abundant. (The CDC did not respond to my request for comment on this latest study.)

A spokesperson for the National Institutes of Health tells The Week, "Our Lyme experts were not independently familiar with the study, and did not feel they could comment on its methods or findings without more information."

The Columbia University Medical Center agrees that it is "highly unlikely" that Lyme disease could be acquired through unprotected sex, and expects that there would be more documented cases if this were the case. William Smith, the executive director of the National Coalition of STD Directors, tells The Week: "We don't believe that this very limited, single study is cause for alarm or cause any changes in the way STDs are treated." He adds, however, that "more work needs to be done on this topic" and regardless, the study is another good reason to listen to your high school gym teacher: "Condoms are an effective prevention strategy for all known STDs."

Update: After this story was published, Benjamin Haynes, a spokesperson for the Infectious Disease Team at the CDC, sent us this statement: "The study had a very small sample size [and] it was not published in a peer-reviewed journal. Additionally, the researchers didn’t specify if validated methods were used to determine that the bacteria were Borrelia burgdorferi [the bacteria that causes Lyme disease]. Since many questions about this project remain, we are unable to answer further questions about it."