Keystone virus makes first jump from mosquitoes to humans with confirmed case in Florida teen, study says

Ashley May | USA TODAY

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A 16-year-old boy, one of the first reported cases of the Keystone virus in humans, is leading researchers to believe the virus could be widespread in North Florida.

Researchers from the University of Florida identified the Keystone virus in the teenager after he visited an urgent care clinic in North Central Florida in August of 2016. Medical professionals suspected he had Zika virus, considering his case was seen during a Zika outbreak, but he didn't. He tested positive for the Keystone virus, spread by a mosquito cousin to the Zika mosquito. He had a rash and fever. A report of his case was published earlier this month in the peer-reviewed medical journal Clinical Infectious Diseases. Authors said this was the first case of the virus in humans, but the Florida Department of Health told USA TODAY that a young child from Sarasota had the virus in 1964.

“Although the virus has never previously been found in humans, the infection may actually be fairly common in North Florida,” J. Glenn Morris, research author and director of the university's Emerging Pathogens Institute, said in a statement.

Morris suggests doctors might not know to look for the virus in patients, which is why more cases might not have been identified.

The virus was first discovered in the Tampa Bay-area in 1964. Since then, animal cases have been found from Texas to the Chesapeake Bay. Symptoms include a rash, mild fever and encephalitis, brain inflammation. The Florida teen did not show signs of encephalitis.

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Doctors have long suspected the Keystone virus might infect people, but there's no specific treatment plan for the virus in humans.

“All sorts of viruses are being transmitted by mosquitoes, yet we don’t fully understand the rate of disease transmission,” Morris said. “Additional research into the spread of vector-borne diseases will help us shine a light on the pathogens that are of greatest concern to both human and animal health.’’

The only known way to prevent the virus is to avoid mosquito bites. The Environmental Protection Agency recommends using insect repellent, wearing long-sleeve shirts and pants, staying inside air-conditioned areas and using screens on windows and doors to prevent bites.

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