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A new tick borne illness that is similar to Lyme disease, with symptoms including fever and muscle pain, are being reported among people in the U.S. for the first time this year.

The bacteria, called Borrelia miyamotoi is relatively new and is one of five newly identified diseases spread by deer ticks. The illness doesn’t have a name yet, and a study published in the Annals of Internal Medicine recently described two patients who showed signs of Lyme disease but did not respond to the common antibiotic treatment with doxycycline.

Lyme disease is caused by the Borrelia burgdorferi bacterium, and B. miyamotoi may be a distant cousin of that strain. So far, cases of B. miyamotoi are relatively rare, but doctors believe more may start to emerge, especially in areas where Lyme disease is common, such as in the northeastern U.S. A study published in the New England Journal of Medicine this past January described 18 people in southern New England and New York who tested positive for the bacterium. The first documented cases of human B. miyamotoi infections occurred in Japan in 2011.

“I think we will definitely see more of it because up to now, people haven’t even know about it. I think that now that they know about it they can look for it,” says Dr. Peter Krause, a senior research scientist in the department of epidemiology and public health at Yale School of Medicine and author of the January study. “It is the very beginning of this disease in humans. We can’t really say now that there is more now then there used to be, because there used to be no cases. I guess you can call it emerging, because there was nothing and now we have something, but it has now been found in humans and it is another disease we have to track.”

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It is also possible that some people infected with B. miyamotoi were misdiagnosed with Lyme disease, since it’s difficult to distinguish the two. Krause says, for example, that while early reports hinted that B. miyamotoi infection did not always cause a rash, as Lyme disease does, cases in Russia showed this wasn’t necessarily true. Among those infected with the bacteria, 10% developed a rash.

So how is the new infection diagnosed? B. miyamotoi is five to 10 times less common than Lyme, but its symptoms are very similar, and there is no test to detect the bug before symptoms start. Once the infection starts, however, fevers caused by B. miyamotoi infection can relapse after resolving, something that doesn’t typically happen in cases of Lyme disease. For now, if a patient complains of fever, muscle pain and headaches and doesn’t respond to doxycycline antibiotics after 24 hours, doctors should order a blood smear test to look for the organism. Technicians can look for the bacteria under a microscope. There are more advanced DNA-based and antibody tests for the bacteria, but only three labs in the U.S. have the capability of performing these analyses. As more cases of non-Lyme diseases caused by tick-carried bacteria grows, however, Krause expects more doctors and labs to recognize and test for the various strains.

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In the meantime, doctors are still learning about how severe B. miyamotoi infections can be, and what long term effect the bacteria can have on health. Researchers reported in another New England Journal of Medicine study that an 80-year-old woman with B. miyamotoi who also had cancer, developed meningitis. “We have known for decades that this type of relapsing fever causes neurological problems like meningitis,” says Krause. “We don’t know the complications of this disease yet, but it is pretty likely neurological problems will be part of this. Whether healthy people will get neurological problems we don’t know, but it is certainly possible. It is one of the many research questions that have to be answered.”

Currently, there is no vaccine for Lyme disease and other related tick-borne illnesses. One vaccine, Lymerix, was pulled from the market after low sales and concerns that it was making people sick. But the Boston Globe reports that Baxter International, Inc. is encouraged by results of its Lyme vaccine, which is being developed with researchers at Stony Brook University and Brookhaven National Laboratory. Other scientists at the University of Rhode Island are also continuing their investigation of ticks in hopes of also developing the first inoculation against Lyme.

In the meantime, doctors are trying to determine how best to treat B. miyamotoi infections. While the two patients in the Annals study did not immediately respond to doxycycline, the antibiotic eventually did control the infection, and other antibiotics such as amoxicillin may also be effective.

But to avoid tick-related diseases altogether, public health officials say it’s best to protect yourself from getting bitten in the first place. Stay out of areas where ticks are known to congregate, such as well-wooded regions and places with high grasses or brush. If you can’t avoid them, wear long sleeves and pants and tuck in any loose clothing. It may be hot, but it’s worth it.