Late Sunday, officials confirmed a San Benito County man who had recently traveled back from Wuhan, China, and his wife have the virus. Both were isolating themselves in their home.
The man arrived at San Francisco International Airport on January 24 and was screened and found to be healthy and asymptomatic, said Dr. Martin Fenstersheib, the county's interim health officer.
The next day, the man developed symptoms including a cough and low-grade fever, Fenstersheib said. A few days later, his wife began showing symptoms as well.
The couple has stayed at home since the man's arrival, Fenstersheib said.
Also Sunday, officials confirmed a woman who recently traveled from Wuhan to Santa Clara County also was found to have the virus. She's the second case in the county -- though officials said the cases are unrelated.
Elsewhere in California, Orange and Los Angeles counties each have had one confirmed case.
Meanwhile, the World Health Organization (WHO) declared the outbreak a public health emergency of international concern last week. A number of countries -- including the US -- began evacuating their nationals on flights from Wuhan, the capital of Hubei province in China where the virus was first detected.
At least 360 people have died and more than 17,000 have been infected in China. Around the world, more than 170 confirmed cases have been reported in more than 20 countries.
On Monday, a spokeswoman for China's Foreign Ministry accused the US government of responding inappropriately to the outbreak and feeding mass hysteria.
"Most countries appreciate and support China's efforts to fight against the novel coronavirus, and we understand and respect them when they adopt or enhance quarantine measures at border entry," Foreign Ministry Spokeswoman Hua Chunying said.
"But in the meantime, some countries, the US in particular, have inappropriately overreacted, which certainly runs counter to WHO advice."
11 cases in the US
The San Benito couple's diagnosis is the second person-to-person transmission of the virus reported in the US.
In Chicago, a woman in her 60s was diagnosed after she returned from Wuhan on January 13. She is in the hospital and doing "quite well," her doctors said.
Last week, the CDC confirmed she had transmitted the virus to her husband, who had not traveled to China. He was in close contact with his wife during a long period of time when she was symptomatic, the Illinois Department of Public Health said.
A student at the Boston campus of the University of Massachusetts was the eight confirmed case. There have been two more confirmed cases of the coronavirus: one in Arizona -- which officials described as an "adult member" of the Arizona State University community -- and one in Washington state -- a man in his 30s who sought treatment after returning from Wuhan.
More US citizens are about to be evacuated
On Monday, US Secretary of State Mike Pompeo said the US will send additional flights to China to evacuate Americans from Hubei Province.
"The exact timing of those we are still coordinating with the Chinese government but we anticipate that they will happen in the next handful of days ... we'll return those American citizens," Pompeo said.
"We may well end up bringing some citizens back from other countries as well. We're working through the details on that."
That announcement came after Health and Human Services Secretary Alex Azar declared the coronavirus a public health emergency in the US.
He said American citizens who were in Hubei Province in the past two weeks "will be subject to up to 14 days of mandatory quarantine."
The CDC ordered a federal a 14-day quarantine for those passengers -- the first such order in more than half a century.
A second evacuation flight from mainland China is set to carry more US citizens out of Wuhan, a US official with knowledge of the matter told CNN. There is still not a definitive time for the plane's arrival in Wuhan.
The first chartered plane arrived in a Southern California air base last week carrying about 200 US citizens -- including diplomats and their families.