In this month's District Report: West Nile virus and birds, bed bug facts, and more.
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District News

  • No West Nile virus was detected in San Mateo County in June. In early July, two dead birds positive for West Nile virus were found in Atherton and Redwood City. The latest WNV results can be found on the District website.
  • No invasive Aedes mosquitoes were detected in San Mateo County in June. The latest invasive Aedes surveillance information can be found on the District website.
  • The District participated in San Mateo County Emergency Response Worker Preparedness Day, San Mateo County Preparedness Day, and the San Mateo County Fair in June.
  • On July 6th the District conducted the first of four helicopter larvicide treatments at Mills Field, Annex Lake, and Sharp Park.
The District asks residents to report dead birds or tree squirrels to the California Department of Public Health West Nile Virus Hotline at 877-WNV-BIRD or online at Specimens that appear to have been dead for less than 24 hours and are in good condition will be tested for West Nile Virus.

West Nile Virus and Birds: What's the Connection?

two crows perched on a streetlamp
Dead crows and other birds are an indication West Nile virus may be circulating locally. Photo: SMCMVCD.

It's a common question for the District laboratory staff: if West Nile virus is transmitted by mosquitoes, why are you testing birds?

Although West Nile virus is transmitted to humans by the bite of an infected mosquito, only birds (never mammals, like humans or horses) can transmit the virus to mosquitoes.This means that birds play an important role in the West Nile virus disease transmission cycle.

Although finding birds infected with West Nile virus is one sign that West Nile virus might be present in mosquitoes in our county, we also know that some bird species fly long distances. They might have been infected by mosquitoes far from our county. Some birds can even get West Nile virus from other birds, either through contact with infected body fluids or by eating other birds that are sick or have died from West Nile virus.

That's why whenever we find a bird infected with West Nile virus, the District's laboratory staff sets 20 mosquito traps throughout a half-mile area around where the bird was found. The traps are collected the next day and any mosquitoes we catch are tested for West Nile virus.

Even if we don't find West Nile virus in the mosquitoes, collecting and testing dead birds for West Nile virus helps us understand the disease transmission cycle in our county and evaluate the risk of human infection.

You can learn more about West Nile virus on the District webpage at or by visiting the California Department of Public Health's West Nile virus page at
Our Work by the Numbers

In June, District technicians:
  • Treated over 43,000 catch basins
  • Conducted 1,315 mosquito larvicide applications
  • Responded to 165 requests for mosquitoes or standing water
  • Removed 59 yellowjacket and wasp nests
  • Conducted 33 rodent inspections
  • Picked up 19 dead birds
  • Delivered mosquitofish to 17 addresses
  • Identified 12 resident-submitted insects
  • Treated 11 acres of marsh
bedbug feeding on human skin

Bed bugs are increasingly common in the US. Photo: CDC.


Don't Let the Bed Bugs Bite

Bed bugs (properly known by their scientific name, Cimex lectularius) have been bugging humans for thousands of years, and have been on the rise in the United States since the 1980s.

Although the mere thought of bed bugs may make your skin crawl, experts say there's no reason to panic: bed bugs don't transmit disease to humans, although they do often cause considerable stress and anxiety. If you think you may have bed bugs in your home, here are a few things you can do:
  • Confirm the infestation. The District can loan you bed bug traps, and will help identify any bugs you catch with them. Other insects commonly mistaken for bed bugs include carpet beetles, fleas, and cockroaches.
  • Don't take it personally. Some people believe bed bugs are associated with poverty and poor sanitation, but this isn't true. Bed bugs will infest clean and dirty homes alike, as long as there are humans there to feed on.
  • Don't do anything drastic. Most household insecticides are not labeled for use against bed bugs and may be ineffective or even dangerous if used improperly. DIY methods of heat treatment can pose a fire hazard. Only use approved products and methods, and don't hesitate to seek professional help.
You can find out more about controlling bed bugs in your home from the US Environmental Protection Agency at, or by contacting the District.

Mosquito Surveillance and Control Data Updates

Visit our Mosquito Surveillance Data and Operations Statistics pages to get the latest data from our mosquito surveillance and control program.

District Financial Information for May, 2016

Visit our Financial Information page for the latest District financial information, including the Consolidated Funds and Profit and Loss as of May 31st, 2016.

Snapshots from the Field

gloved hands swabbing a crow's throat
Laboratory staff test a sick crow for West Nile virus at Peninsula Humane Society.
man and woman in protective suits and hoods
Interns Justin Loman and Nancy Yip learn about rodent-borne disease surveillance.
helicopter and truck
Technician Jim O'Brien prepares for a helicopter larvicide treatment at Annex Lake.
herd of goats
Technician Sean makes friends with a herd of goats being used to clear brush in San Bruno.
San Mateo County Mosquito and Vector Control District
Protecting public health since 1916

1351 Rollins Rd. | Burlingame CA 94041
(650) 344—8592 |

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San Mateo County Mosquito and Vector Control District · 1351 Rollins Rd. · Burlingame, CA 94010 · USA

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