https://www.sfgate.com/bayarea/article/coronavirus-Santa-Clara-Bay-Area-San-Francisco-15021074.php

By Amy Graff, SFGATE

Updated 5:32 pm PST, Friday, January 31, 2020

The Santa Clara County Health Department said Friday that a resident of the county tested positive for the new coronavirus, marking the first case in the Bay Area. This is the third case in California, with two others reported in Southern California.

While health officials said the risk to Bay Area residents remains extremely low, the recent news may have some residents asking questions.

What is coronavirus?

The viral respiratory illness spreading rapidly in China is a new kind of coronavirus that scientists have never observed in humans before. Coronaviruses are a large family of viruses, some of which cause the common cold. Others have evolved into more severe illnesses, such as SARS and MERS, although so far the new virus does not appear to be nearly as deadly or contagious.

How many people are impacted?

The number of confirmed cases worldwide has risen to 9,800, with the majority of those cases in China, according to the World Health Organization. More than 200 people have died.

The World Health Organization has declared novel coronavirus a global health emergency, and the U.S. Department of Health and Humans Services has declared a public health emergency in the United States. But the center of the outbreak is in Wuhan, a port city of 11 million in the Hubei province of China. The Chinese government has quarantined the city, and restricted travel to and from several other cities, including the capital, Beijing.

About 200 cases have been confirmed across two dozen countries outside China, including Australia, Cambodia, Canada, Finland, France, Germany, India, Italy, Japan, Malaysia, Nepal, Philippines, Russia, Singapore, Sri Lanka, Sweden, the Republic of Korea, Taiwan, Thailand, United Arab Emirates, the United Kingdom and Vietnam. The Centers for Disease Control and Prevention (CDC) is updating this list daily.

There are seven cases in the United States: three of them in Southern California, two in Illinois, one in Washington state and another in Arizona.

For comparison, between November 2002 and July 2003, the outbreak of SARS in southern China infected 8,098 people, resulting in 774 deaths reported in 17 countries. The majority of cases were in in mainland China and Hong Kong.

What's the mortality rate?

"There’s a lot we don’t know about coronavirus, and one is the case fatality rate -- what percentage of patients will die of the illness," said Dr. Chiu of UCSF. "It does appear based on the data available so far that this appears to be less deadly than SARS at 2 to 3 percent, and for SARS, it was about 10 percent. This is still a more severe disease than the flu. It has a mortality rate of .o1 percent."

Chiu added that at this early stage in virus and with most cases in China, it's difficult for researches to pin down the mortality rate. He said in China, officials have been focused on the public health response and they're only now able to start analyzing data.

Who is the person who tested positive in Santa Clara County?

The first Bay Area case involves an unnamed adult male who is a resident of the county and who traveled to Wuhan, China. He showed symptoms after returning home, and has been self-isolating at home. The patient is stable and hasn't been sick enough to be hospitalized. He was seen at a local clinic. For privacy reasons, other details on the patient aren't being released. The CDC and county health officials are monitoring anyone this person has come into contact with, but the number is thought to be low, because he has stayed at home.

Now that someone in the Bay Area has coronavirus, am I at a higher risk? 

"Although we do understand this confirmed case may raise concern, this one case, in fact, doesn't change the risk for the general public," said Dr. Sara Cody, a health officer with Santa Clara County. "Our assessment is that the public at large is still at low risk, because this case was careful to self-isolate at home since the time he returned from China."

The San Francisco Public Health Department echoed Cody's message, saying the risk in the city remains low. "San Francisco has zero cases of novel coronavirus at this time," the public health department said in a statement. "If a case is confirmed in San Francisco, the Department of Public Health will announce it, in cooperation with the U.S. Centers for Disease Control and Prevention and the California Department of Public Health."

What's more, Dr. Charles Chiu, a professor of laboratory medicine and infectious disease at UC San Francisco, said "I think the risk in the U.S. is still close to zero. We haven’t seen any evidence of sustained transmission currently, but I emphasize currently because that may change. Although we have confirmed cases, they have been coming from returning travelers from Wuhan, or a household member of a returning traveler."

MORE: World stocks skid as virus fears spook markets, hit tourism

What are the symptoms?

The virus can cause fever, coughing, wheezing and pneumonia. The incubation period is thought to be two weeks. But it's also a heavy flu season, and some of the symptoms are similar.

"If you have traveled to Wuhan and are experiencing a fever or lower respiratory illness, such as a cough or trouble breathing, contact your medical provider by phone," advised Balram. "Let them know your symptoms and travel history before going to the ER.  You want to make contact first."

What's the origin of coronavirus?

The exact origin is currently unknown, but Dr. Chiu said it likely originated from bats. "We know this because most coronaviruses are thought to originate from bats," he said. "SARS originated from bats and coronavirus about 80 percent identical to SARS. It's about 90 percent identical to a bat virus."

The transmission of a disease from a bat directly to a human is very rare and Chiu said it's more likely another animal is the intermediary but researchers aren't certain which one yet. There was one paper pointing to snakes, but Dr. Chiu said the research is still fuzzy. "I think right now it’s up in the air," he said. "There’s likely an intermediary reservoir that’s likely to be an animal, but we don't know yet."

How can I stay safe?

"There are things people can do to make themselves safer, and by far the most effective way to do this is really good hand-washing," said Dr. Susan Philip, San Francisco's deputy health officer and director of communicable disease prevention. "We don’t do that as much as we should, especially when riding public transit. We don’t realize how much we touch surfaces and then our faces."

Should I start wearing a mask to protect myself?

There's currently no need for residents to wear masks when they leave their homes, according to Dr. Philip. But if a mask puts you at ease, there's likely no harm in using one.

You should consider wearing a mask if you're coughing or have a fever to stop the spread of viruses. While there continues to be a low risk of coronavirus transmission, flu and cold viruses are rampant at this time of year.

"Masks do have a role," Dr. Philip said. "If people are sick, we prefer they stay home. But if they do have to go out, then wearing a mask is a great idea to prevent the spread of germs to people around you."

Should I start stocking up on food in case of an outbreak in the Bay Area?

"We don’t think there’s any reason to stock up on food," said Dr. Philip. "We don’t advise people to panic. If people are really worried, the best thing is to stay informed by checking the CDC website where you find updated information. You can also check in with your county health department."

What's the United States doing to prevent spread into the country?

The CDC is screening passengers on direct and connecting flights from Wuhan at multiple airports including Atlanta, Chicago, New York City, San Francisco and Los Angeles.

The United States is imposing a travel ban on foreign nationals who have been in China in the past 14 days.

What's the Bay Area doing to prepare for potential local cases?

San Francisco Mayor London Breed said Monday that the city has activated the Emergency Operations Center and is working with local, state and federal agencies to be ready to respond, if necessary. Other Bay Area counties are doing the same.

ALSO: Are you in danger of catching the coronavirus? 5 questions answered

Amy Graff is a digital editor with SFGATE. Email her: agraff@sfgate.com.