For Healthcare Providers
Cache Valley virus is a Bunyamwera serogroup virus, in the genus Orthobunyavirus, family Peribunyaviridae. The virus is widely distributed in mosquito populations throughout North America and parts of Central America. Only rare human cases have been reported, including from North Carolina, Missouri, Wisconsin, and New York. All cases have occurred from late spring through early fall. The transmission cycle is not well understood but the virus has been isolated from a broad range of mosquito species (including Anopheles, Culiseta, Coquillettidia, and Aedes species) and the main vertebrate hosts are likely ungulates (e.g., deer, cattle, horses and sheep).
Clinical Evaluation and Disease
Healthcare providers should consider Cache Valley virus infection in patients with acute fever, meningitis, or encephalitis during spring through fall, particularly when tests are negative for more common infections such as herpes simplex virus, enteroviral, and other arboviral infections (e.g., West Nile, St. Louis encephalitis, La Crosse, Jamestown Canyon, or eastern equine encephalitis virus infections).
Initial symptoms of Cache Valley virus infection are non-specific, including fever, headache, nausea, vomiting, fatigue, and sometimes rash. Severe diseases presentations range from aseptic meningitis to fatal encephalitis.
Healthcare providers should consider Cache Valley virus and other arboviral infections in patients with acute fever, meningitis, or encephalitis during spring through fall in the United States, particularly when tests are negative for other more common infections (e.g., herpes simplex virus or enteroviral infections).
Diagnostic methods include serological testing of serum or cerebrospinal fluid (CSF), and viral culture performed on serum, CSF, or tissue specimens. In fatal cases, testing of autopsy specimens can be performed. Healthcare providers should contact their state or local health department for assistance with Cache Valley virus testing, which is done at CDC and some state health departments.
Treatment and Prevention
There is no specific treatment for Cache Valley virus disease; clinical management is supportive. The case fatality rate cannot be determined based on the small number of reported cases. Some patients who recovered from acute Cache Valley virus infection later died from complications of illness.
The best way to prevent Cache Valley virus infection is to avoid mosquito bites. Protective actions people can take include using insect repellent and wearing long-sleeved shirts and pants when outdoors. More information about reducing exposure to mosquito bites is available on the prevention page.