ATLANTA – A mosquito-borne illness that has been mainly limited to white-tailed deer throughout North America is emerging as a more frequent cause of human disease, according to a report from the Minnesota Department of Health.
The Jamestown Canyon virus (JCV), a member of the California serogroup of bunyaviruses likely transmitted to humans through the bite of an infected Aedes-species mosquito, was first detected in a human in Minnesota in 2013. Due to suspicion that cases were being missed by an assay in use at the time in Minnesota, which had relatively poor sensitivity for detecting Jamestown Canyon virus, an enzyme immunoassay specific to JCV was put into use in 2014 to test serum and cerebrospinal fluid specimens submitted for other arboviral testing. Subsequently, an additional six cases were identified, Elizabeth Schiffman reported at the International Conference on Emerging Infectious Diseases.
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Between May and October of 2014, 141 serum or cerebrospinal fluid samples from 107 unique patients were tested. Of these, 20 samples from 17 patients initially tested positive for JCV; further testing at the Centers for Disease Control and Prevention in Atlanta confirmed the findings in 7 specimens from 6 patients, said Ms. Schiffman, an epidemiologist at the Minnesota Department of Health, St. Paul.
Findings from other specimens were pending at the time of her presentation.
The initial patient was a 49-year-old man who had generalized symptoms, including myalgia, fatigue, and nausea for about week, who then was hospitalized after experiencing sudden onset of fever, disorientation, and aphasia. Viral encephalitis was suspected, and specimens sent to the Minnesota Department of Health, then to the CDC, were positive for JCV. The other patients with confirmed JCV ranged in age from 11 to 77 years (median, 56).
Illness onset was between late May and early September, and patients presented with symptoms typical of mosquito-borne illnesses, including fever, fatigue, myalgia/arthralgia, and/or headache, although clinical syndromes varied among individuals.
“Three patients were classified as having meningoencephalitis, three had fever without neurological involvement, and one patient developed acute flaccid paralysis,” Ms. Schiffman said, adding that six of the seven patients were hospitalized with duration ranging from 4 to 20 days (median, 7 days), and three were discharged to acute rehabilitation facilities for further care.
Although only three patients were classified as having neuroinvasive disease, five of the seven reported symptoms suggestive of some neurologic involvement, ranging from mild confusion and altered mental status, to aphasia, ataxia, and seizure, she said.
An additional case from 2002 was retrospectively identified, she noted.
Although JCV has been known to cause disease in humans since the 1970s and has been nationally notifiable since 2004, it is rarely reported. In fact, only 31 human cases were reported in the United States from 2000 to 2015, she said, adding that the disease is likely underrecognized, particularly in more mild forms.
“It is expected that continued testing and increased awareness among health care providers of JCV as a possible cause of human disease – particularly viral encephalitis – will likely aid in the identification of additional cases in the future,” she said.
This work was funded by the Epidemiology and Laboratory Capacity Cooperative Agreement with the CDC.