New 'Heartland' virus discovered in sick Missouri farmers

Two men in Missouri who became severely ill after sustaining tick bites were found to be infected with a new type of virus, according to a study from the Centers of Disease Control and Prevention (CDC).

Both men were admitted to hospitals after experiencing high fevers, fatigue, diarrhea and loss of appetite. They were originally thought to be suffering from a bacterial infection, but doubts arose when they didn't improve after being treated with antibiotics.

Further tests revealed their blood contained a new virus, which the researchers dubbed the Heartland virus. It belongs to a group called phleboviruses, which are carried by flies, mosquitoesor ticks, and can cause disease in humans.

While the genetic material of Heartland virus appears similar to that of other phleboviruses, the particular proteins it produces are different enough to call it a new species, said study researcher Laura McMullan, a senior scientist at the CDC.

Because the Heartland virus causes such general symptoms, it could be "a more common cause of human illness than is currently recognized," the researchers wrote in the Aug. 30 issue of the New England Journal of Medicine.

More studies are needed to identify the natural hosts of the virus, learn how many people are infected with it and find risk factors for infection, McMullan said.

Because both men experienced tick bites shortly before they became ill — one man, a farmer, reported receiving an average of 20 tick bites a day — the researchers said it's likely that the Heartland virus is spread by ticks, although more research is needed to confirm this.

The new virus's closest relative is another tick-borne phlebovirus, called SFTS virus, which was identified last year in China, and causes death in 12 percent of cases.

The Missouri men, who were both infected in 2009, recovered after 10 to 12 days in the hospital, although one of the men has reported recurrent headaches and fatigue in the two years since his hospitalization.

The researchers suspect a species of tick commonly found in Missouri, called Amblyomma americanum, is one of the hosts of the Heartland virus.

For now, taking precautions to prevent tick bites is the best way to avoid the virus, McMullan said. To prevent tick bites, the CDC recommends using repellents that contain 20 percent or more DEET, as well as avoiding wooded areas or areas with high grass.

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