With new West Nile virus cases reported in California and Washington state, health officials are reminding the public that it’s not too late in the season to catch the mosquito-transmitted disease.
With above average temperatures impacting much of the United States despite the official end of summer, mosquito activity continues across much of the country, extending West Nile virus season into the fall.
Most cases of West Nile virus occur during the summer months from June through September, when infected mosquitoes are most active and spread the disease through their bites. However, warmer weather in autumn can extend mosquitoes’ breeding season, and thus, West Nile virus season. The Centers for Disease Control and Prevention (CDC) has reported at least 875 human cases in 47 states so far this year. While more than 60% of those reported infections have involved neuroinvasive illness, severe symptoms occur in less than 1% of infected individuals. Most human cases of West Nile go undetected and show no symptoms, with cases of severe illness more likely to be reported.
In response to an increasing number of West Nile virus cases in the Los Angeles area, the Los Angeles County Department of Public Health announced on September 25, 2017, that it will be conducting more mosquito spraying treatment and launching a public health campaign dedicated to warning area residents about mosquito transmission of West Nile and Zika viruses. The campaign, titled “Not Just a Bite,” comes as the West Nile case count in Los Angeles County has continued to rise, with 98 cases total so far this year. County health officials confirmed on Monday that the county’s West Nile deaths had increased to seven area residents; one of those victims included Julie Shepherd, 84, who was diagnosed with West Nile earlier in the month and died this week following complications from the virus.
Across the state of California, there have been 174 human cases and eight deaths from West Nile this year. “Starting today, Public Health will deploy 100 teams across the county to deliver packets to over 20,000 local businesses, community buildings, houses of worship and schools with health education materials and easy steps everyone can take to prevent bites,” said Los Angeles County Department of Public Health director Barbara Ferrer, PhD, MPH, MEd, in a recent statement. “Since we are currently in the peak of mosquito season, we are working together with our cities, the vector control districts and regional partners to inform people about the risk of diseases from mosquitoes.”
Elsewhere in the country, two human West Nile virus cases likely acquired in Washington’s Spokane County prompted officials from the Spokane Regional Health District (SRHD) to remind area residents to avoid exposure to mosquitoes in order to prevent bites. The two cases both involved men — one in his fifties and one in his sixties – whose infections were confirmed by the Washington State Public Health Laboratory. Area health officials believe a third case reported in the county had been acquired in another state. These are the first West Nile infections of 2017 in the state, which reported nine cases in 2016.
Despite the approaching end to West Nile season, health officials in Spokane are warning the public about the dangers of the virus. “Although the vast majority of people with West Nile virus will not develop severe illness, some are at higher risk of severe disease, including those who are 60 years of age or older, those with compromised immune systems, or those with underlying medical conditions,” said SRHD health officer Bob Lutz, MD, MPH.