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California Experiences Autumn WNV Pressure

California’s improved 2020 numbers against West Nile Virus took a step backward, beginning with the last full week of September.

After a total of 33 confirmed human cases were reported in Week 39, reported transmissions settled down for the week ending October 2. Reported cases in Week 40 were limited to three: one each in Madera, Tulare, and Orange Counties. Pressure picked back up again the following week, however, as 19 additional cases were reported in the October 9 Arbobulletin. Included in that count were the first human WNV cases of 2020 in Kern and Tehama counties.

Two WNV fatalities were reported in Merced County, bringing the state’s total of 2020 WNV deaths to four. Merced county officials reported that both of the new cases involved people over 50 that had underlying health conditions.

That brings California’s 2020 number of WNV cases up to 114. The good news is that the state remains down versus last year by just over 21%, continuing the downward trend in YTD case. This comes at a time when the number of WNV-positive dead birds reported has gone from 193 at this time in 2019 to 277 in 2020, an increase of about 50%. This implies activity is high, but locations around humans are being better protected.