New mosquito-borne virus found in humans for first time

Keystone virus first identified in Tampa

GAINESVILLE, Fla. – A mosquito-borne virus that can cause a rash and mild fever has been identified in humans for the first time, according to University of Florida researchers.

Keystone virus was first identified in 1964 and has been found in animal populations on coastal regions from Texas to Chesapeake Bay.  

Dr. J. Glenn Morris, director of the UF Emerging Pathogens Institute, said that the virus has long been suspected in humans for years.

“Although the virus has never previously been found in humans, the infection may actually be fairly common in North Florida,” he said. 

In fact, 19 to 21 percent of people tested in Tampa Bay had Keystone virus antibodies, according to a 1972 article in the American Journal of Tropical Medicine and Hygiene. 

“It’s one of these instances where if you don’t know to look for something, you don’t find it,” Morris said.

Keystone virus is part of a virus group, known as the California serogroup of viruses, UF Public Health and Health Professions professor and Emerging Pathogens Institute member John Lednicky said. 

These viruses can cause encephalitis, or brain swelling, according to Lednicky.  

The first human case was announced in a June 9 report, titled Keystone Virus Isolated from a Florida Teenager with Rash and Subjective Fever: Another Endemic Arbovirus in the Southeastern United States?” Lednicky is the first author of the report and Morris is a co-author.

A teenage boy went to an urgent care clinic in North Central Florida with a rash and fever symptoms in August 2016, according to the report. Laboratory samples were taken because of concern about Zika virus. However, he tested negative for Zika or related viruses. 

When UF researches did viral cultures using the patient samples, they found the virus grew in mouse brain cells, suggesting the virus could infect brain cells. The patient did not report symptoms of encephalitis.

Morris said that more research is needed to better understand the prevalence of vector-borne diseases, or diseases caused by parasites, viruses and bacteria transmitted by mosquitoes, sandflies, triatomine bugs, blackflies, ticks, tsetse flies, mites, snails and lice.

“All sorts of viruses are being transmitted by mosquitoes, yet we don’t fully understand the rate of disease transmission,” he 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.’’

In the meantime, Morris said that the risk of mosquito bites can be reduced by using mosquito repellent when and where mosquitoes are present.