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Low Risk of Zika Virus in SMC

posted Feb 9, 2016, 4:53 PM by MPFPD Community Emergency Response Team
From the San Mateo County Mosquito and Vector Control District:

Lately, the District has been getting a lot of questions about Zika virus and whether residents of San Mateo County are at risk. We’d like to give you a little more information about what we're doing to reduce the risk Zika virus and other risks associated with invasive Aedes mosquitoes in San Mateo County, and how you can help us keep your community healthy. 

At this time, the risk of Zika virus infection in San Mateo County is extremely low. Although the mosquito that transmits Zika virus, Aedes aegypti (the yellow fever mosquito), has been found in our county, it is NOT widespread or common. Without a large population of these mosquitoes, and with only a few cases of travel-acquired Zika virus in our county at any given time, local transmission of Zika virus is very unlikely. 

Invasive Aedes aegypti mosquitoes were discovered in San Mateo County in 2013 by the District laboratory’s ongoing invasive mosquito surveillance program. We don’t know how they arrived, but we suspect they came as mosquito eggs on plants or containers from an area in the US where Aedes aegypti is common. Since 2013, the District has been working to eradicate these invasive mosquitoes from our county. This includes house-to-house inspections for invasive mosquitoes, intensive mosquito population surveillance, and treatment or elimination of standing water where mosquitoes may breed. 

Although the risk of Zika virus in our county is extremely low at this time, it is still important to avoid introduction of invasive mosquitoes to our county and to limit their spread where they have been introduced. Keeping invasive Aedes mosquitoes out of our county reduces not only the risk of Zika virus, but of other diseases transmitted by invasive Aedes mosquitoes, like dengue, chikungunya, and yellow fever. 

You can help keep our communities free of invasive Aedes mosquitoes by following a few simple guidelines: 

- Check your property for existing standing water and containers where water may collect after rain. Invasive Aedes mosquitoes prefer man-made containers (flower pots, buckets, bottles, cans, etc.) and can develop in containers as small as a soda bottle cap. Any container can become a breeding ground for mosquitoes. 

- Remove or overturn any containers where water collects. Containers that cannot be removed must be emptied and scrubbed weekly to remove mosquito eggs. Invasive Aedes eggs can survive drying out, so it is not enough to empty the containers – they must also be scrubbed. 

- Avoid bringing plants, pots, or other outdoor items from areas where invasive Aedes are established (including central and southern California, Arizona, Texas, and Florida). If bringing items from these areas, please empty and scrub all containers to remove mosquito eggs. 

- If you notice mosquitoes biting during the day, please contact the District so we can check your area for invasive Aedes mosquitoes. Unlike most of our native mosquito species, invasive Aedes mosquitoes bite during the day. 

Although the risk of Zika virus infection in San Mateo County is minimal at this time, travelers to areas affected by the Zika virus epidemic are encouraged to consult the latest guidance from the CDC (www.cdc.gov/zika) and take appropriate precautions. 

For more information on Zika virus, visit www.cdc.gov/zika. For more information on invasive mosquitoes in San Mateo County, visit www.smcmvcd.org/invasive. To report suspected invasive Aedes mosquitoes or to receive help with any other mosquito-related issue, call (650) 344-8592. 


Megan Caldwell 
Public Health Education and Outreach Officer 
San Mateo County Mosquito and Vector Control District