What you need to know about coronavirus in the Bay Area

Passengers wear face masks as they arrive on a flight from Asia at Los Angeles International Airport on January 29, 2020. Passengers wear face masks as they arrive on a flight from Asia at Los Angeles International Airport on January 29, 2020. Photo: Mark Ralston, AFP Via Getty Images Photo: Mark Ralston, AFP Via Getty Images Image 1 of / 72 Caption Close What you need to know about coronavirus in the Bay Area 1 / 72 Back to Gallery

As coronavirus fears spread through the Bay Area and beyond, Californians have myriad questions about the outbreak.

While health officials said the risk to Bay Area residents remains low, recent news may have some residents asking questions. We've contacted experts on a variety of topics:

What is coronavirus?

The viral respiratory illness that originated 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.

How many people are impacted?

The number of confirmed cases worldwide has risen to close to 80,000, with the majority of those cases in China, according to the World Health Organization. More than 2,500 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 2,000 cases have been confirmed across about 50 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 60 cases in the United States.

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. Charles 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."

Researchers around the world are analyzing the data on cases as cases spread and it has been difficult to pin down the mortality rate. It does, however, seem as though elderly patients have an increased risk of dying of the virus and children are at a lower risk for complications and death.

What's the deal with the "unknown origin" patient in Solano County?

On Feb. 26, the CDC announced the first patient, a resident of Solano County, with an infection of unknown origin had been identified.

"At this time, the patient’s exposure is unknown,'' the CDC said in a statement. "It’s possible this could be an instance of community spread of COVID-19, which would be the first time this has happened in the United States. Community spread means spread of an illness for which the source of infection is unknown. It’s also possible, however, that the patient may have been exposed to a returned traveler who was infected.''

Up until this case, the patient count in the United States has included only people who traveled back from outbreak areas in China, or their spouses. However, Travis Air Force Base, where some coronavirus patients from the cruise ship Diamond Princess were quarantined, is located in Solano County.

There are nine cases in the Bay Area. Seven of those are travel related, one is due to close household contact with a spouse who traveled to China, and the source of the most recent one has yet to be identified, according to the California Department of Public Health.

Now that individuals in the Bay Area have coronavirus, am I at a higher risk?

In Solano County where the first case of unknown origin was announced on Feb. 26, health officials said the risk still remains low. "Solano Public Health is working with local, state and federal partners to identify, notify and monitor individuals who may have been exposed to the virus," the county's public health department said in a statement. "While this is considered a serious public health threat, the risk to Solano County residents and the general public is low at this time."

The California Department of Public Health said in a statement, "This is a serious public health concern. We are actively working with the Centers for Disease Control and Prevention (CDC), with local governments, and health care providers across the state to protect your health."

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.

What's the origin of coronavirus?

The exact origin is currently unknown, but experts believe it came from animals.

"Most coronaviruses are thought to originate from bats," Chiu 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 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 does the virus spread?

Similar to the transmission of the flu, COVID-19 spreads through droplets expelled when someone coughs or sneezes, or by direct person-to-person contacts, such as by hand and or kissing. It remains unclear how long it can survive in inanimate objects and whether it can be transmitted by touching things like handles touched by an infected person.

"Currently, it’s unclear how easily or sustainably this virus is spreading between people," according to the CDC.

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."

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

San Francisco Mayor London Breed declared a "local emergency" for coronavirus, despite no confirmed cases in the city. Although a dramatic-sounding declaration, all it currently does is allow for more emergency preparedness, including freeing up funds and reassigning city staff to temporarily roles.

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 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," 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?

No.

"We don’t think there’s any reason to stock up on food," said 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."

"The best thing to do is have your emergency kit," said Mary Ellen Carroll, executive director of S.F.'s Department of Emergency Management. "I hope everyone in the Bay Area has a kit and some reserves for any emergency such as an earthquake. But we're not suggesting people stockpile extra food.

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