Two of the patients were on the Grand Princess cruise ship in Mexico , and the other patient had close contact with another COVID-19 patient in another jurisdiction.
At a press conference on Friday, health officials say all three individuals are in home isolation and do not require hospitalization. The individuals' health are being monitiored by public health according to Centers for Disease Control guidelines, officials said.
This brings the county to four known positive cases of novel coronoavirus.
Officials also say it's still unknown how the first positive case in Contra Costa County contracted the virus.
CCHS is recommending that people who are higher risk from COVID-19, including adults over 50 and people with certain underlying medical conditions, should avoid mass gatherings, such as parades, sporting events or concerts.
Health officials said school sporting events in the county do not need to be cancelled at this time. Officials said not to panic, but to take precautions in protecting themselves.
CORONAVIRUS IN CALIFORNIA: What to know about COVID-19, how it's affecting San Francisco Bay Area
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