Americans are too worried about the new coronavirus that's spreading rapidly across China, former White House health advisor Dr. Ezekiel Emanuel told CNBC on Thursday

"Everyone in America should take a very big breath, slow down, and stop panicking and being hysterical," said Emanuel, who served during Barack Obama's presidency. "We are having a little too much histrionics on this."

Alex Azar, current secretary of Health and Human Services under President Donald Trump, also said later Thursday on CNBC that the risk to Americans remains low.

Chinese officials on Thursday increased their confirmed coronavirus cases to more than 8,000, though some experts believe the number to be much larger. The death roll rose to 170.

Health officials across the world having been putting efforts in place, such as travel restrictions and isolation, to try and stop the virus from spreading. It was first discovered in the Chinese city of Wuhan in Hubei province in December.

The Centers for Disease Control and Prevention has confirmed five cases of the coronavirus in the United States, with 92 pending tests, as of Wednesday. Other countries around the world are also reporting isolated cases.

"I'm actually pretty confident that we're going to restrict the spread in the United States and people should remember not to panic," said Emanuel, vice provost for global initiatives at the University of Pennsylvania. "We need to be a little sober about it, even in China."

The Wuhan virus, which causes flu-like symptoms, is not spreading through human-to-human contact in America, Dr. Nancy Messonnier, director of the National Center for Immunization and Respiratory Diseases, said Monday.

But Dr. Mike Ryan, executive director of the World Health Organization's health emergencies program, said Wednesday that the coronavirus has spread to a handful of people through human-to-human contact outside of China.

On Thursday afternoon, the CDC and Illinois public health officials confirmed the first U.S. person-to-person transmission of the coronavirus. The new patient is the spouse of a Chicago woman who brought the infection back from Wuhan.

The WHO is set to reconvene this week to decide whether to declare the coronavirus a global health emergency.

The new virus has now infected more people in China than were sickened there during the 2002-2003 SARS epidemic. That severe acute respiratory syndrome outbreak, which also originated in China, killed 774 people.

"I think we need to put it into context, the death rate is much lower than for SARS," Emanuel said.