Health officials said the person tested positive Tuesday afternoon and is expected to be confirmed by the Centers for Disease Control & Prevention (CDC) in the coming days.
According to county officials, the patient is being treated at an unknown hospital in Contra Costa County and in critical condition.
The patient has had underlying health conditions that possibly lead to his current condition.
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The patient had no known travel history and no known contact with someone with a confirmed case of the novel coronavirus.
Contra Costa Health Services is investigating to identify anyone who may have had close contact with the patient.
This is the fourth Covid-19 patient that's been treated in Contra Costa County.
Three infected patients from the Diamond Princess cruise ship had been treated in Contra Costa County hospitals.
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Two have since been cleared and released, while one is still being treated.
Stay with ABC7 News on this developing story.
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