By Stephanie Stahl

PHILADELPHIA (CBS) — The world is reacting as the coronavirus spreads. The first case of coronavirus with no immediate links to worldwide travel or a related illness has been identified in a patient hospitalized in California.

There are still a lot of unanswered questions about this newly revealed patient, but it’s an indication the coronavirus is spreading in the United States. It’s what health officials predicted would happen.

“There’s probably other cases out there in the community that we don’t know about,” said Dr. Dean Blumberg, with UC Davis Health Pediatric Infectious Diseases.

Doctors at the UC Davis Medical Center are concerned the patient might be the first of many infected by someone else in the general population.

The patient was transferred last Wednesday, already intubated and on a ventilator. The individual wasn’t tested for coronavirus until Sunday and the results came back positive just Wednesday.

It’s the first case of what doctors are calling “community transmission.”

“It suggests that we don’t know where they got it from, so the person who exposed them probably exposed others,” Blumberg said.

On Wednesday night, President Donald Trump tried to ease fears over the coronavirus outbreak.

“The risk to the American people remains very low,” Trump said.

Trump tapped Vice President Mike Pence to head the administration’s response.

“We are ready to adapt and we are ready to do whatever we have to,” Trump said.

Federal health officials, however, warned more infections are likely.

“The trajectory of what we’re looking at over the weeks and months ahead is very uncertain,” said Dr. Anne Schuchat, principal deputy director of the Centers for Disease Control and Prevention.

Pennsylvania Secretary of Health Dr. Rachel Levine also said Wednesday that the state will be ready.

“To date, the Wolf administration has activated the Department of Health’s Emergency Health Operation Center to allow for an enhanced and coordinated response,” Levine said.

Symptoms of coronavirus are similar to the flu, with fever and respiratory issues, but there is growing evidence the virus can be spread by people who have no symptoms, raising concerns there could already be more cases in the United States that haven’t been detected.

The best prevention is to wash your hands, cover your coughs and stay home when you’re sick.

Stephanie Stahl