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October 2023 Newsletter

West Nile Virus 2023 Season

Computer generated image of a silhouette of ten birds on their backs (dead)

As of October 10, West Nile virus has been detected in 10 dead birds from throughout San Mateo County.  West Nile virus has not yet been detected in any mosquito or sentinel chicken samples in San Mateo County in 2023. Learn more HERE.

West Nile virus is widespread throughout California this summer. If you are traveling, even within the state, be sure to use insect repellent to prevent mosquito bites (learn more here). For information about West Nile virus throughout California, visit


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