The New Tick Danger
Credit: M Phillips David / Getty Images

This summer, Lyme disease is poised to be as threatening as ever. The Center on Disease Control predicts 300,000 new cases, particularly in hotspots along the Northeast coast and upper Midwest, though Lyme cases have been recorded – and are still expected – in every U.S. state.

Breadth alone makes Lyme alarming. But there's a new tick-borne disease that poses a risk to anyone spending time outdoors: A bacteria called Borrelia miyamotoi. Scientists estimate that 10 percent of ticks in the Northwest have Borrelia, and this April, researchers in the Bay area found more ticks carrying this new bug than Lyme, and they were in nearly every park – not just heavily wooded areas, but in grass too. (This was after San Francisco health officials assured the city earlier this spring that it didn't have a tick problem.) "In a way, this bacteria is more insidious," says infectious disease physician Peter Krause, M.D., of Yale, who first discovered Borrelia miyamotoi in the U.S. last summer. "While an adult female can't transmit Lyme to offspring, she can pass on Borrelia; that means a baby tick the size of a pin point can bite and infect you."

This new bacteria causes a disease that mimics the symptoms of Lyme – total-body aches, incredible fatigue – but instead of having the classic bull's-eye rash, you'll experience a fever that can spike to 104 degrees. The fever is relapsing, so you may think you're getting better, but then you fall ill all over again. Left untreated, it can morph into a disease that causes cardiac, neurologic, and arthritic problems.

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Researchers have known for years that this disease was in the same blacklegged ticks that carry Lyme – ticks have a soup of hundreds of diseases inside them – but it's just in the past year that they've discovered it can infect humans, says Richard Ostfeld, a medical ecologist at the Cary Institute of Ecosystem Studies in New York State. "What makes this relapsing fever so scary is that, unlike Lyme, there's no widely available test for it; if you get sick, you're likely to go undiagnosed and untreated."

Vigilantly checking for ticks is still your best defense, and if you find one, removing it immediately. "Don't panic," says Krause. "If you have the Lyme rash, get prompt treatment and you'll do well. If you don't see a rash, don't test positive for Lyme, yet have all the symptoms, ask your doctor to check that you might have the Borrelia bacteria, or even another tick-borne disease." If your doctor isn't a tick specialist, you may want to find someone who is. A John Hopkins study found that some 20 percent of people don't respond to the typical round or two of antibiotics; an experienced doctor will know to prescribe more of the drugs. "Taking more antibiotics – what's most effective at killing any tick-borne illness, including this new bacteria – may be less dangerous than the alternative: developing a debilitating disease," says New York State Lyme disease physician Kenneth Liegner.

There is one promising development: Researchers at the University of Rhode Island are working on an anti-tick vaccine that, once administered, could prevent the insects from biting you and spreading any diseases. But the vaccine is still a year or more out.