Fox News medical analyst Dr. Marc Siegel joined "Tucker Carlson Tonight" Monday to give an update on the coronavirus that originated in the Chinese city of Wuhan and has spread to several other countries, with at least five reported cases in the United States.

"I’ve been studying contagions for a really long time, and I’ve never seen anything like this," Dr. Siegel said.

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Late Monday, the Chinese government said that at least 106 deaths had been attributed to the coronavirus, with more than 4,500 cases confirmed in the country.

Earlier Monday, the State Department urged Americans to reconsider traveling to Wuhan and said it had ordered all non-emergency U.S. personnel and their families to leave China.

Siegel blamed Chinese authorities for just now beginning to impose quarantines and travel restrictions in and around Wuhan a full year after the virus was first reported, calling their inaction "reckless and really, really scary."

He also said he "has reason to believe" that the actual number of cases in China is far greater than the number the local authorities have reported, which could impact how the U.S. Centers for Disease Control and Prevention (CDC) responds to the rapidly spreading contagion.

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"The numbers are suddenly skyrocketing. For months there was word coming out of China that people were getting sick from a strange illness and people were dying," Siegel said. "Are they really on all of the death certificates [from] this virus? Do we know people that had this? Or do they think they had the flu?

"We don’t know if this is more contagious or deadly than the flu. We need to know that. We are studying these five people [in the U.S.] very, very carefully. But that’s what should’ve been done in China from the beginning. And it wasn’t. I am positive that there are thousands and thousands of cases that never came to light here."

Siegel praised the CDC, calling them a "shining light in the darkness."

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"They have looked at 110 cases already, found five -- all of whom have traveled from Wuhan -- and ruled out 32 cases that did not have it. They are teaching us as we go now how contagious this is," he said. "I am very proud of our own government CDC. Not what is going on in China."

Reiterating his warnings against traveling to China until the virus is contained, Siegel said U.S. citizens may be allowed to enter China, but that their access out of the country is not guaranteed.

"Viewers need to know," Siegel said. "You can get there and China can say that you can’t go back. 'You can’t leave. We are not letting you out. We are afraid that you might have the Wuhan coronavirus.'"

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"So," he continued, "I would tell everybody unless they absolutely have to, to stay out of China. And I’m not trying to say, by the way, that all parts of China are equally affected. That is not my point. But you could go there and they could decide, 'Whoops, now you’re in the area we are worried about,' and not let you go home."