2 California coronavirus cases confirmed: What you need to know

Passengers wear masks to protect against the spread of the Coronavirus as they arrive at the Los Angeles International Airport, California, on January 22, 2020. - A new virus that has killed nine people, infected hundreds and has already reached the US could mutate and spread, China warned on January 22, as authorities urged people to steer clear of Wuhan, the city at the heart of the outbreak. less Passengers wear masks to protect against the spread of the Coronavirus as they arrive at the Los Angeles International Airport, California, on January 22, 2020. - A new virus that has killed nine people, ... more Photo: Mark Ralston / AFP Via Getty Images Photo: Mark Ralston / AFP Via Getty Images Image 1 of / 29 Caption Close 2 California coronavirus cases confirmed: What you need to know 1 / 29 Back to Gallery

Over the weekend, two Southern California residents were diagnosed with coronavirus, the third and fourth individuals in the United States testing positive for the pneumonia-like virus that originated in China.

What's more, Alameda County Public Health Department said last week it has been investigating less than 10 people from the county who have recently traveled to Wuhan, China for coronavirus. Alameda County Public Health Department spokesperson Neetu Balram said the patients under investigation present a range of cases, and at this point, there are no confirmed cases in Alameda County, nor the Bay Area.

While the risk to Bay Area residents remains extremely low, the recent news developments 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 has risen to more than 4,500 and the majority of those are in China. At least 106 people have died. For perspective on the speed of the spread, the National Health Commission said 769 new cases were confirmed in the 24 hours through midnight Sunday.

Wuhan, a port city of 11 million in the Hubei province, is at the center of the outbreak, and the Chinese government has quarantined the city. It has also restricted travel to and from several other cities, including Beijing.

Small numbers of cases have been found in Thailand, Taiwan, Japan, South Korea, the U.S., Vietnam, Singapore, Malaysia, Nepal, France and Australia.

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

The first patient in Southern California was diagnosed in Orange County on Jan. 25 and the second was identified in Los Angeles County on Jan. 26. A case was also confirmed in Arizona's Maricopa County on Jan. 26.

The first two U.S. cases were confirmed last week: A Chicago woman in her 60s tested positive on Jan. 24, and a 30-something man in Washington State on Jan. 21.

Am I at risk as a Bay Area resident?

"At this time, residents of the Bay Area are at low risk at becoming infected with the coronavirus unless they have traveled to Wuhan in the last 14 days or come into contact with someone who has traveled there," said Balram.

Commenting on the national risk, the CDC's Dr. Nancy Messonnier said, "CDC believes that the immediate risk to the American public continues to be low at this time, but the situation continues to evolve rapidly."

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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."

How can I stay safe?

It's always smart to practice precautions that protect you from catching a cold. Wash your hands frequently, especially after touching highly used surfaces such as handrails and doorknobs.

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 five major airports in Atlanta, Chicago, New York City, San Francisco and Los Angeles.

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

San Francisco Mayor London Breed said Monday the city has activated the Emergency Operations Center and is working with local, state and federal agencies to be ready to respond if necessary.

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

The Associated Press contributed to this report.

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