Officials said further information about the individual would not be released for reasons of medical privacy.
Friday's announcement comes shortly after the US declared a public health emergency because of the new virus. "Our assessment is that the public at large is still at low risk, because this case was careful to self-isolate at home for the entire time since he returned from China".
The patient was seen at a local clinic and hospital, but was never sick enough to be hospitalized.
"A second case is not unexpected". He now remains at his home as he is not sick enough to be hospitalized, according to Dr. Sara Cody, director of Santa Clara County's Public Health Department.
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Japan and Germany also advised against non-essential travel to China and Britain did as well, except for Hong Kong and Macao. China's National Health Commission said in its daily report on Saturday that 1,795 patients were in critical condition.
Since his return on January 24, officials said, the man left his home twice to seek medical care, but has not been hospitalized and is being treated in his home.
"We are now reaching out to anyone he may have had contact with to assess whether they may have been exposed to the novel coronavirus", said Cody. Anyone who has had contact with the man and his household members will undergo a 14-day quarantine.
All foreign nationals who have travelled to China in the last two weeks and aren't immediate family members of USA citizens or permanent residents will be temporarily banned from entering the US.
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Infected people have been reported in 29 provinces of China, along with the special administrative regions of Hong Kong and Macao. The Chicago woman returned from Wuhan a week ago and has mostly stayed in her home since returning from that visit.
A man has tested positive for the Wuhan coronavirus in the San Francisco Bay Area, bringing the number of US confirmed cases of the virus to seven as three major USA airlines announced they would halt air travel to mainland China in an effort to stop the spread. The first death outside China from the new virus was recorded Sunday in the Philippines.
Santa Clara County officials offered more details on the case during a Friday afternoon press conference.
Almost 200 Americans who were evacuated from Wuhan are under a 14-day quarantine at a military base outside Los Angeles - the first by the government in half a century. So far, six other cases of the virus have been reported in the USA, including two cases in Southern California, two in IL, one in Arizona and one in Washington state.
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She has since been released from quarantine after tests showed she did not have the same kind of virus found in China. Coronaviruses originate in bats but can infect a number of animals, and from there jump to humans.