Virus Levels & Exposure Risk in San Mateo County
While there are many ways to quantify COVID-19 risk in San
Mateo County, including the CDC’s Community
Level, which measure impacts on local health care systems,
County Health stresses that there is still significant
community transmission of COVID in San Mateo County. Virus levels
are 2-5 times higher than the low levels of March 2022.
While cases are gradually decreasing, the Omicron
variants remain prevalent and residents face
a risk of exposure.
Virus transmission levels are estimated by County
Health by reviewing many sources, including data
from local laboratories, hospitals, PCR tests, schools,
The number of reported cases severely underestimates the
level of virus in San Mateo County because so many people use
rapid antigen tests (that are not reported to health departments)
and few use PCR tests (which are reported).
To prevent infections and severe disease in San Mateo County
and the Bay Area region, it’s important to be current
with vaccinations and
boosters (including the new, updated booster),
get tested if you have symptoms, and wear a mask to prevent
exposure and spread, especially if you have symptoms, a
positive test, or a known exposure to someone with COVID-19.
The California Department of Public Health and San Mateo
County Health recommend best practices to
protect individuals and communities.
- Get the updated, bivalent booster to prevent infections from
the Omicron strain circulating in San Mateo County
- The best way to prevent infection is to wear a high-quality
mask (N95, K95) in indoor public spaces, such as grocery stores
improved ventilation throughout indoor spaces when possible
and avoid closed spaces with poor ventilation
- Stay home if you feel sick and get tested right away
- Follow the California Department of Public Health (CDPH)
isolation and quarantine
- If you are immunocompromised or at high risk for severe
disease, consider wearing a mask in indoor public
spaces, have a plan for rapid testing (e.g. access to
at-home tests), and
talk to your healthcare provider about whether you are a
candidate for treatments like oral antivirals, pre-exposure
prophylaxis (PrEP), and monoclonal antibodies
- Distribute and administer vaccines to achieve high community
vaccination coverage and ensure health equity
improved ventilation in public indoor spaces
- Ensure access to testing, including through point-of-care and
at-home tests for all people
- Communicate with organizations and places that serve people
who are immunocompromised or at high risk for severe
disease to ensure they know how to get rapid testing
- Ensure access and equity in vaccination, testing, treatment,
community outreach, support services for disproportionately
- Advise businesses, venue operators, event hosts and
other organizations to consider requiring
patrons to wear masks inside their facilities
Importance of Indoor Ventilation
Proper indoor ventilation while gathering inside reduces the
spread of COVID-19. Proper ventilation includes opening windows
and doors to bring fresh air in or using an air filtration
system (please check air quality during fire season prior to
opening windows and doors). Using an air filtration system
indoors can reduce COVID-19 particles in the air by 72%
after an hour of use. Leaving a single window open for
an hour can reduce COVID-19 particles by 44%. Practicing
these simple steps when gathering indoors, can significantly
reduce the risk of spreading COVID-19. For further
guidance on indoor ventilation from the CDC, visit Improving
Ventilation in Your Home.
CDC Indoor Ventilation Tips
The risk of getting COVID-19 varies according to individual
susceptibility and the number of virus particles to which a
person is exposed. The fewer virus particles in the
air, the better. Adjusting ventilation settings can reduce
the number of particles and infections.
Bring as much fresh air into your home as
- Open doors and windows as much as you can to bring in
fresh, outdoor air, if it’s safe to do so.
- If opening windows or doors is unsafe, consider other
approaches for reducing virus particles in the air, such as using
air filtration and bathroom and stove exhaust fans.
Filter the air in your home.
- Set the fan to the “on” position instead of “auto” when
you have visitors.
- Change your filter every 3 months or according to
Use fans to improve air flow.
- Place a fan as close as possible to an open window blowing
outside, which helps get rid of virus particles.
- Point fans away from people.
Consider using a portable air cleaner, particularly when
you have guests.