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

Trustworthy information about COVID-19

Risk Factors for COVID-19 Infection

SARS-CoV-2 is a coronaviruses, as are viruses that cause the common cold - and shares many of the same risk factors. It is spread by infected people, who often don't know they are infected because they have no symptoms (asymptomatic) or because their own symptoms have not yet developed. (However, unlike the common cold, people infected with SARS-CoV-2 can infect others for 2-3 weeks after they start feeling symptoms.) Broadly speaking, our chances of catching this disease are greater if we:

  • are exposed many times, more frequently and for more extended periods of time (sometimes called having a higher "viral load");
  • have lower immunity in general (have a chronic disease or cancer, but also people who smoke); 
  • are in close physical proximity to each other (in some childcare settings, larger households, nursing homes, care settings, shelters, or prisons); and / or
  • don't have the resources to slow the spread of disease (poor access to healthcare, clean water, or housing).

Unfortunately, these factors also seem to raise the chances of having a more severe case of COVID-19.

Health Conditions that Make People More Vulnerable

While there is still much to learn about COVID-19, as of this writing, there is general agreement that these underlying medical conditions are associated with more severe COVID-19 symptoms are:

  • COPD
  • serious heart conditions (chronic heart failures, past heart attacks or cardiomyopathies
  • chronic kidney  disease
  • type II diabetes
  • sickle cell anemia
  • obesity

People with these conditions may also be more at risk for severe COVID-19: (it's still unclear)

  • smoking, vaping, or other lung conditions (moderate to severe asthma, pulmonary fibrosis)
  • other vascular or blood conditions (chronic high blood pressure, thalassemia, cerebrovascular disease)
  • dementia
  • liver disease
  • type I diabetes
  • immunocompromised (by cancer or HIV)


See the links below for instructions (including disease-specific action plans) on how to protect yourself if you have any of these conditions.

Vulnerable Populations

As we learn more about COVID-19, it appears that although people of all ages can transmit the virus, disease symptoms tend to be more severe in older people. While older adults tend to also have chronic health conditions, or to be living in care centers, the number of fatalities among healthy seniors is higher than can expected from those factors alone.

At the same time, more younger people are catching COVID-19 (while the good news is that more younger people recover, the bad news is that many have serious damage or long-term effects from the disease). And while it's rare for young children to have symptoms of COVID-19, many are asymptomatic and can spread it to older people in their households, schools, or daycare.


At the same time, case data from many different states in the U.S. show that Black and Latinx people are more likely to catch COVID-19 and to have more serious illness. Not all, but some Native reservations in the U.S. have been among the hardest hit regions in the U.S., too.

Vulnerable jobs: Heathcare workers are one of the most at-risk professions for severe COVID-19 illness. By treating sick patients, they have much greater exposure to the novel coronavirus than most people (a much higher viral load).  Grocery store workers, cashiers, bus drivers and taxi drivers also have higher rates of infection than the general public, for similar reasons.

The CDC, state, and local health departments have directives on what employers and employees should do to avoid spreading the novel coronavirus.

People with disabilities (physical, cognitive, behavioral or developmental) that make their activities of daily living more difficult for them - or who are dependent on other people for help with their activities of daily living - are also more vulnerable. See the links below for protections (including disease-specific action plans) for these conditions.

Because children can have little or no symptoms while they have active COVID-19 infections, they can spread the novel coronavirus as widely as they spread the common cold (another coronavirus). Unlike children down with the common cold, though, children with SARS-CoV-2 can infect other people for 2-3 weeks after they catch it, even if they show no symptoms of the disease at all.

Rarely, some children sick with COVID-19 experience multisystem inflammatory syndrome (MIS-C), which can be quite serious - but is treatable.

A group of epidemiologists and public health professionals (not affiliated with any government agency) has published this summary of advice on assessing the risk of catching and spreading SARS-CoV-2 by unvaccinated people, especially younger children:

COVID risk levels for kids


Not having a stable home makes it extremely difficult to take care of one's health, especially during this pandemic. While services for the homeless are greatly needed, they need extra precautions as well.

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