June 18, 2018: A virus first found in Tampa Bay-area mosquitoes that appears to cause a rash and mild fever has been identified in humans for the first time, according to University of Florida researchers.
The findings are yet another indicator of the range of diseases that can be caused by mosquito bites in Florida, in keeping with a recent study by the U.S. Centers for Disease Control and Prevention that highlighted the almost doubling of vector-borne disease cases in the United States since the early 2000s.
“Although the virus has never previously been found in humans, the infection may actually be fairly common in North Florida,” said J. Glenn Morris, M.D., M.P.H., director of the UF Emerging Pathogens Institute and corresponding author of the report on the virus published June 9 in the journal Clinical Infectious Diseases.
“It’s one of these instances where if you don’t know to look for something, you don’t find it,” he added.
The virus, called “Keystone virus” after the location in the Tampa Bay area where it was initially identified in 1964, has been found in animal populations along coastal regions stretching from Texas to the Chesapeake Bay.
While there were no reports of human infection until now, human infection has long been suspected. A 1972 article in the American Journal of Tropical Medicine and Hygiene reported Keystone virus antibodies in 19 to 21 percent of the people tested in the Tampa Bay region.
The new report, titled “Keystone Virus Isolated from a Florida Teenager with Rash and Subjective Fever: Another Endemic Arbovirus in the Southeastern United States?,” says a teenage boy went into an urgent care clinic in North Central Florida with a rash and fever symptoms in August 2016, during the Zika virus epidemic in Florida and the Caribbean. Because of concerns about Zika, laboratory samples were collected from the patient; however, all studies were negative for Zika or related viruses.
Unexpectedly, UF researchers did find Keystone virus when they did viral cultures from the patient samples. Although the patient did not report symptoms of encephalitis, researchers report that the virus grew well in Neuro-2A cell cultures. Neuro-2A cells are mouse brain cells, and the ability of the virus to grow in these cells suggests that Keystone virus can infect brain cells, and may pose a risk for brain infections.
“This virus is part of a group commonly known as the California serogroup of viruses,” said John Lednicky, Ph.D., a research professor in the UF College of Public Health and Health Professions’ department of environmental and global health and a member of the Emerging Pathogens Institute. Lednicky is the first author of the report.
“These viruses are known to cause brain inflammation or encephalitis in several species, including humans,” he added.
Jamestown Canyon virus and La Crosse encephalitis virus are two of the most commonly known viruses in the California serogroup.
Due to the likelihood that Keystone virus is a common though previously unidentified pathogen among people in the region, Morris emphasized the need for additional research into the prevalence of vector-borne diseases in the United States.
“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.’’
Morris also stressed the importance of minimizing the risk of mosquito bites by using mosquito repellent at times and places where mosquitoes are present.