In what is almost certainly a medical first, a physician from my hometown of St. Joseph, Mo., has identified a new viral disease thought to be transmitted by ticks. The virus is related to hantaviruses, which have recently caused at least two deaths at Yosemite National Park, but so far only two confirmed cases have been observed. Because the two farmers who contracted the virus live 60 miles apart, however, researchers from the Centers for Disease Control and Prevention suspect there are probably many more unrecognized cases.
The two patients were first seen by Dr. Scott M. Folk, an infectious diseases specialist at Heartland Regional Medical Center in St. Joseph. Both were hospitalized for fever, fatigue, headache, nausea and diarrhea. The two cases were suspected to be outbreaks of ehrlichiosis, a bacterial infection, but antibiotics failed to help the patients. Both ultimately recovered on their own with supportive care from the hospital. Full recovery required a couple of months.
Folk sent blood samples from the two men to virologist Stuart T. Nichol and his colleagues at the CDC. The researchers reported this week in the New England Journal of Medicine that the samples contained a previously unseen virus. Sequencing of its genome showed the virus, which the researchers call the Heartland virus, is a member of the Bunyaviridae family of RNA viruses, which includes hantaviruses. The new virus is a member of the group called phleboviruses; the 70 distinct members of this family are most often transmitted by sand flies and mosquitoes. Only one member of the group has previously been shown to be transmitted by ticks -- the “severe fever with thrombocytopenia syndrome virus” identified last year in central and northeastern China.
Nonetheless, the team thinks the Heartland virus is also transmitted by ticks, particularly Amblyomma americanum, the Lone Star tick, which is the most common tick in the region. The first patient, a 57-year-old man who lives on a farm in northwestern Missouri, found a small tick on his abdomen and began developing a fever the following day. The second patient, a 67-year-old man who lives on a different farm in the same area, received an average of 20 tick bites per day for two weeks while building a fence on his property. The last tick bite was noted about a week before his hospitalization.
The team is now examining ticks and farm and wild animals in the region looking for a host of the virus. Because the symptoms of infection are so common, the researchers wrote, the virus “could be a more common cause of human disease than is currently recognized.”