Health officials have confirmed that two California residents have been diagnosed with the coronavirus despite no known contact with an infected individual and no recent travel overseas.

“This new case indicates that there is evidence of community transmission, but the extent is still not clear,” said Dr. Sara Cody, Health Officer for Santa Clara County and Director of the County of Santa Clara Public Health Department, where the second patient resides.

The first case of community transmission of the coronavirus in the United States was announced Wednesday when the U.S. Centers for Disease Control and Prevention confirmed a woman from Solano County had tested positive for the virus. The second confirmed case was announced Friday when a woman from Santa Clara was found to have the virus.

“This is a fluid situation but we have plans and protocols in place for public health events like this to protect the health and safety of Californians and the state’s visitors. We are actively working with the CDC, with local governments, health facilities, and health care providers across the state to respond as new cases are identified,” said Dr. Sonia Angell, Director of the California Department of Public Health and State Health Officer.

The cases of the two infected women marks an escalation of the worldwide outbreak in the U.S. because it means the virus could spread beyond the reach of preventative measures like quarantines, though state health officials said that was inevitable and that the risk of widespread transmission remains low.

The first case prompted Solano County to declare a local emergency on Thursday to bolster its response efforts in identifying, screening and following up with individuals potentially exposed to the virus.

The Solano County woman first went to a hospital in Vacaville on Feb. 15 and stayed there for three days until her worsening condition led to her transfer to UC Davis Medical Center in Sacramento. It was another four days before she was tested by the CDC for the coronavirus because she didn’t fit the criteria the agency had been using for travel.

"We are taking this situation seriously and are taking steps necessary to protect the health and safety of Solano County residents," said Dr. Bela Matyas, Solano County Health Officer. “It is important to recognize that we have moved from containment to mitigation. We are investigating potential exposures and ensuring that proper evaluation and care are provided if they become sick.”

The Santa Clara woman is an older adult with chronic health conditions who was hospitalized for a respiratory illness. Her infectious disease physician contacted the Public Health Department to discuss the case and request testing for the novel coronavirus. The County of Santa Clara Public Health Laboratory received the specimens Thursday and performed the testing. Since receiving the results Thursday night, the department has been working to identify contacts and understand the extent of exposures.

The Stanislaus County Health Services Agency posted on their website that there are no confirmed cases of coronavirus in the county. Two people from the county have been tested for the virus and the tests came back negative. The health department’s website shows 11 county residents are under public health supervision because of a known risk of having been exposed to the coronavirus, also now referred to as COVID-19.

“We understand that there are concerns and understandably so,” the health agency stated on social media. “This is a new virus and we are still learning from it. However, the health risks remain low in our county and the general public in California.”

The new virus comes from a large family of what are known as coronaviruses, some causing nothing worse than a cold, but others cause more serious illnesses such as SARS. It causes cold- and flu-like symptoms, including cough and fever, and in more severe cases, shortness of breath. It can worsen to pneumonia, which can be fatal. The Centers for Disease Control and Prevention stated that symptoms can appear as quick as two days and up to 14 days after exposure.

The viruses are common in many different species of animals, including camels, cattle, cats, and bats and it’s rare that animal coronaviruses can infect people and then spread between people, such as the case with this current coronavirus.

First detected in December, the virus is believed to have originated in a type of wild animal sold at a Wuhan, China market to be consumed as food.

The CDC said person-to-person spread occurs mainly via respiratory droplets from when an infected person coughs or sneezes, similar to how influenza and other respiratory pathogens spread. These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled into the lungs. It’s currently unclear if a person can get the novel coronavirus by touching a surface or object that has the virus on it and then touching their own mouth, nose, or possibly their eyes.

In the United States and many other nations, public health officials are turning to guidelines written for pandemic flu and discussing the possibility of school closures, telecommuting and canceling events.

As with any virus, especially during the flu season, health officials remind people there are a number of steps to take to protect your health and those around you:

— Washing hands often with soap and water for at least 20 seconds;

— Using an alcohol-based hand sanitizer if soap and water are not available;

— Covering your coughs and sneezes with your arm;

— Frequent cleaning of doorknobs, light switches, and other commonly touched areas with disinfectant wipes;

— Avoiding contact with people who are ill; and

— Staying away from work, school or other people if you become sick with respiratory symptoms like fever and cough

The Associated Press contributed to this report.