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Fox News medical contributor Dr. Marc Siegel told "Tucker Carlson Tonight" Wednesday that "lockdowns don't work" once a virus becomes widespread as the debate over when and how to continue reopening the country rages on.

"Lockdowns don't work if there is already a lot of virus in the area, in the community, in the state, the country," Siegel said.

The NYU Langone internist referenced what he called a "shocking" JPMorgan study released Wednesday indicating that states and countries where lockdowns were implemented have had a higher rate of COVID-19 cases than locations that remained open throughout the pandemic.

"South Dakota, which was never locked down, has had almost no cases over the last several days," Siegel noted.

"In Hong Kong ... they have a very ineffective government. You know why they have been able to do so well with only four deaths from COVID-19?" Siegel said, "Because the people behaved. They knew how to do social distancing. It wasn't locking down. Locking down definitely doesn't make the problem better ... if there is already a lot of virus."

Siegel urged state leaders to ease restrictions as soon as possible, citing concerns of an uptick in "deaths of despair."

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"You know what locking down does? Locking down destroys our health care system to the point where we have more heart attacks [in patients] that are not going to the hospital now," he said. "More strokes that are not going to the hospital now. More cancer that is not being screened. People say they are afraid to go to the emergency room right now. "

On Tuesday, more than 600 doctors signed on to a letter calling on President Trump to end the so-called "national shutdown," calling stay-at-home orders keeping businesses closed and kids home from school a "mass casualty incident" with "exponentially growing health consequences."

"Suicide, drug abuse, alcoholism," Siegel said, "there are going to be more deaths of despair than from the virus itself."

Fox News' Tyler Olson contributed to this report.