Warner Media chairman Jeff Zucker said Monday that employees of CNN and other networks would be limited in their travel between continents to cases in which there is a "most necessary, business-critical need" amid a worldwide outbreak of the deadly coronavirus.

Zucker said CNN will continue to cover big political events such as the Democratic debates, while Turner Sports, which includes TNT and TBS, will cover the upcoming NCAA men's basketball tournament, but under a new level of caution.

“We will work to be sure that our staffing needs are met, but limit any participants that are not absolutely critical to getting our content out or meeting basic revenue-generating needs,” Zucker wrote in a memo to staff. “Some of this can be determined simply by using good judgment, and we encourage you to consider your travel with that in mind.”

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Zucker also noted that travel in the U.S. should be done “only if absolutely necessary,” while internal meetings “should be conducted by phone or via teleconference."

“Nothing is more important than your well-being," he added. "While some of these protocols may seem inconvenient, they are being taken out of an abundance of caution to keep you all safe."

It is not known how long the restrictions will remain in place.

The memo comes as the coronavirus death toll rose to six in the U.S., with all occurring in Washington state.

--This report was updated at 2:59 p.m.