Emerging mosquito-borne bunyaviruses in Canada

California serogroup and Cache Valley viruses are arboviruses (tick- and mosquito-borne pathogens) belonging to the genus Orthobunyavirus (Family Bunyaviridae). Although the majority of exposures to these viruses result in asymptomatic or mild infections, both California serogroup and Cache Valley viruses can cause febrile and neurological diseases similar in nature to those associated with infections by West Nile virus. California serogroup and Cache Valley viruses are widely distributed across North America and circulate in a number of vertebrate hosts and mosquito vectors, including several species of Aedes and other non-Culex mosquitoes. The Jamestown Canyon and snowshoe hare viruses are the most common kind of California serogroup viruses found in Canada and have been identified throughout the country. These potential pathogens may be contributing to a higher burden of illness than previously recognized and should be considered as part of the differential diagnosis for febrile and neuroinvasive disease during the mosquito season. Diagnosis can be made by requesting a diagnostic panel at the Viral Zoonoses program at the National Microbiology Laboratory. To decrease the risk of infection, education about these viruses and the importance of personal preventive measures is warranted.