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 identified, including cases reported 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.

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.

Diagnostic Testing and Reporting

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.

Healthcare providers should contact their state or local health department for assistance with Cache Valley virus testing. They can assist you with determining if samples should be sent to the CDC Arbovirus Diagnostic Laboratory for further testing.

Contact your state or local health department for assistance with diagnostic testing. They can assist you with determining if samples should be sent to the CDC Arbovirus Diagnostic Laboratory for further testing.

ALL RESULTS WILL BE SENT TO THE APPROPRIATE STATE HEALTH DEPARTMENT. Specimens should be submitted to CDC through state health departments.

Cache Valley virus disease is a nationally notifiable condition. All cases should be reported to local public health authorities in a timely manner. Reporting can assist local, state, and national authorities to recognize outbreaks and to implement control measures to reduce future infections.

Treatment and Prevention

There is no specific treatment for Cache Valley virus disease; clinical management is supportive. Patients with severe meningeal symptoms often require pain control for headaches and antiemetic therapy and rehydration for associated nausea and vomiting. Patients with encephalitis require close monitoring for the development of elevated intracranial pressure, seizures, and inability to protect their airway.

No Cache Valley virus vaccines are available for use in humans. In the absence of a vaccine, prevention of Cache Valley virus infection depends on personal protective measures to decrease exposure to infected mosquitoes. This includes using EPA-approved insect repellent, wearing long-sleeved shirts and pants, treating clothing and gear with 0.5% permethrin, and taking steps to control mosquitoes indoors and outdoors. More information about reducing exposure to mosquito bites is available on the prevention page.

Cache Valley virus can be transmitted through blood transfusions. People with confirmed Cache Valley virus infections should not donate blood for 4 months after their illness. Cache Valley virus infections temporally associated with blood transfusion should be reported promptly to the appropriate state health department.