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Coronavirus and COVID-19 Information: Santa Clara County and Bay Area, California

Trustworthy information about COVID-19

Break the Chain of Transmission

What is Social Isolation? Self-Quarantine?

To slow down the spread of coronaviruses, we are asked to "socially distance" ourselves, and to "self-quarantine" if it's possible that we have been in contact with the novel coronavirus. What do these terms mean, exactly? The U.S. Centers for Disease Control gives these definitions in an Interim US Guidance for Risk Assessment on March 7, 2020:

"Distancing means remaining out of congregate settings, avoiding mass gatherings, and maintaining distance (approximately 6 feet or 2 meters) from others when possible."

Congregate settings are crowded public places where close contact with others may occur, such as shopping centers, movie theaters, stadiums.

Isolation means the separation of a person or group of people known or reasonably believed to be infected with a communicable disease and potentially infectious from those who are not infected to prevent spread of the communicable disease. Isolation for public health purposes may be voluntary or compelled by federal, state, or local public health order.

Quarantine in general means the separation of a person or group of people reasonably believed to have been exposed to a communicable disease but not yet symptomatic, from others who have not been so exposed, to prevent the possible spread of the communicable disease.


If I suspect I have been exposed, what should I do?

If you don't know for sure, quarantine yourself until you can be tested. (See our page on Testing for links to locations and dates of free swab tests in the Bay Area.)

Testing too soon after exposure will give false results, so wait  5-8 days after when you thought you might be exposed to get a swab test. (An analysis of people who were diagnosed with COVID-19 and who had a known time of exposure found that 97% of those cases had an incubation period of between 2-12 days.)

If you cannot get tested but suspect you could be infected, the current recommendation is to quarantine for 14 days.  

Wear a Face Covering in Public

Wear a face mask or covering whenever you are in public. Face coverings are fairly effective at limiting how far we could spread the virus, and somewhat effective at limiting how much we are exposed to other people's viruses.

risk with & without masks

Infographic from University of Kansas Health System

Not all masks are equally effective, as this video explains:

There have been several different Orders and recommendations about face coverings since mid-March; to clear the confusion, on June 18 the California Department of Public Health issued an update that requires throughout the state wearing a covering over their mouth and nose when in public settings. Specifically,

Wear a face covering or mask when:

  • inside (or in line to enter) any indoor public space;
  • outdoors in any public space, whenever you cannot keep at least 6 feet away from anyone who does not live in the same household (this includes outdoor activities like hiking, biking, running);
  • waiting for, or using public transportation (including ride sharing, taxis, and tow trucks);
  • at work, if coworkers or members of the public are ever present in the same space.

There are some exemptions, including:

  • children under 2 years old, 
  • while communicating with someone who is deaf or hard of hearing, if necessary, and 
  • (when dining in restaurants is permitted), while eating at a restaurant, so long as physical distance and airflow requirements are being followed.

See the text of the June 18 mandate for more details.

new What about wearing double masks?

Will that give more protection from the newer, extra-contagious versions of SARS-CoV-2? We don't know. It's possible this would give more protection, but whether that's better than a well-fitting cloth mask with a filter insert is unknown. What is important, as this video explains, is that the layer closest to the face makes a tight seal all around the mouth and nose.

Most particle masks (N95, KN95, KN94) are not intended for constant use or reuse. Wearing a cloth mask over a particle mask, and washing that after every use, could extend the life of the particle mask somewhat.

Disinfectants and Hand Sanitizers

We've all heard the advice to "wash your hands with soap for 20 seconds". Some even have lists of songs that are at least 20 seconds long to use to in timing how long to wash.

If we cannot wash with soap and water, using hand sanitizer (sometimes called hand scrub) is second-best. Use enough sanitizer that all hand surfaces are cleaned. To be effective against the novel coronavirus, though, the solution should be at least 60% isopropyl or ethanol alcohol ("anti-bacterial" ingredients will not do anything to virus).

DO NOT USE sanitizer containing methyl alcohol, which is toxic. The U.S. FDA has found methyl alcohol in over 60 brands of hand sanitizer; for a list of brands of hand sanitizer to avoid, or to read about the science behind this advice, see:

But what about washing surfaces in our homes, schools, or offices? COVID-19 is spread primarily through the air, only very rarely by touching surfaces where the virus lands. In April 2021, the CDC revised its guidance to reflect that, and stated that in most cases regular cleaning is sufficient block transmission (so long as masks are worn and hands are washed before touching face or mask).

Longer-Term Strategies for Reopening California

Isolation, quarantine, sheltering at home, and distancing restrictions - these avoidance restrictions are important, but they won't cure this disease.

Historical data, including the worldwide influenza epidemic of 100 years ago, shows us that's what is likely to happen if restrictions are released all at once, all over the country. That's why coordination between state, regional, and local health authorities is so important.  Conditions at the county level are what decides which stage and how many businesses need to be closed. This is to lower the chance that infectious local hot spots would cause a spike in new infections. 

California state government created stages for re-opening in the Resilience Roadmap, revised in late August as the Blueprint.  Various metrics - the number of new cases, the number of people tested, the numbers of people hospitalized and the numbers of deaths - are used to measure if and  when a county could move to the next step in the re-opening process. And to decide when counties need to lock back down again. The state monitors each county's performance on those key criteria, and a county cannot open further (move up to the next stage) until its metrics meet those requirements.

Advice on Travel

COVID-19 is pandemic; people are infected all over the world. Travel was - and is - the main way this disease is spread from community to community, from my town to your town, and between countries. 


As of January 29, 2021, the federal government requires everyone to wear a mask when using transit (including air travel).

While public transit is a necessity in the traffic-congested Bay Area, there's also concern about possible spread of the novel coronavirus on buses and trains. Routes may be changed during the pandemic, and policies may change - check the websites relevant for you frequently.

To slow the spread of the novel coronavirus in the United States, the Centers for Disease Control publishes updates, recommendations for travelers, and news about travel restrictions.

Be aware of the travel restrictions in place, both for the destination and for when you return home. (Both San Francisco and Santa Clara Counties currently have mandatory quarantines when traveling; see box for Bay Area Closures and Restrictions Currently in Place on this page for those details.

Need to change tickets? See the roundup of U.S. airline policies below.

Besides considering the risks of traveling to and from your destination, also investigate what's done at  your lodging to limit exposure (ask about hotel or B&B cleaning practices) and calculate the risks of the kinds of activities you plan to include on the trip.

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