Each summer, surveillance for West Nile virus ramps up as the weather warms. The District uses three surveillance techniques to guard against West Nile virus (WNV) outbreaks: trapping adult mosquitoes, collecting dead birds, and monitoring two sentinel chicken flocks.

The California Department of Public Health opens the Dead Bird Hotline in April each year to receive reports of dead birds. Dead bird reports are often the first sign that West Nile virus is active in an area, and the reports help track West Nile virus throughout the year.

Adult mosquito abundance began to rise in April, which is typical in the spring, but overall numbers remain low. It is important for the public to continue to dump out standing water and to contact us in the case of biting mosquitoes.

We have been receiving numerous calls from residents of Foster City, Redwood Shores, and eastern San Mateo. Swarms of non-biting midges are being mistaken for mosquitoes and causing concern. Luckily, although midges are annoying, these midges do not bite. The District does not control non-biting midges because they do not pose a threat to public health. Sometimes there are also mosquitoes in an area, and so if you are being bitten, please report to the District so that we can follow-up with mosquito trapping and searching for mosquito breeding sources.