Health authorities in British Columbia have confirmed the presence of invasive mosquitoes and a virus capable of causing brain inflammation in humans in the Sea-to-Sky region above Vancouver. This discovery followed an investigation that was prompted by a series of childhood encephalitis cases.
Following three pediatric encephalitis cases in August 2024, researchers initiated a search for the invasive mosquitoes in the area spanning from Squamish to Pemberton. Anya F. Smith, a senior scientist at the B.C. Centre for Disease Control (BCCDC), reported that they identified two mosquito species carrying the California serogroup virus. This group of mosquito-borne viruses has the potential to lead to encephalitis and meningitis in humans.
Among the mosquitoes found to be carrying the virus was the northern house mosquito, originally from Africa, Asia, and Europe. The virus levels detected were deemed low, preventing the team from pinpointing the specific strain of the California serogroup virus present.
Stefan Iwasawa of the BCCDC highlighted the significance of the study in shaping responses to future infections. He emphasized the potential for increased mosquito exposure due to rising temperatures from climate change. Understanding the mosquito species prevalent in British Columbia and the viruses they may carry will aid in preparedness and response strategies related to California serogroup virus infections.
According to a joint statement from the BCCDC, Vancouver Coastal Health, the University of B.C., and the Provincial Health Services Authority, there were 15 documented cases of the virus in British Columbia between 2009 and 2024, with no reported cases in the Sea-to-Sky corridor in 2025. The statement reassured the public that the risk of severe illness from the California serogroup virus in British Columbia is minimal.
