WASHINGTON -- The Defense Department has ordered commanders at all of its installations worldwide to stop announcing publicly new coronavirus cases among their personnel, as the Pentagon said Monday that more than 1,000 U.S. military-linked people had been sickened by the virus.

The order issued by Defense Secretary Mark Esper on Friday is meant to protect operational security at the Defense Department's global installations, Jonathan Hoffman, the Pentagon's chief spokesman, said in a statement Monday. He said Defense Department leaders worried adversaries could exploit such information, especially if the data showed the outbreak impacted U.S. nuclear forces or other critical units.

"Unit level readiness data for key military forces is information that is classified as a risk to operational security and could jeopardize operations and/or deterrence," Hoffman said in the statement. "If a commander believes that [the coronavirus] could affect the readiness of our strategic deterrent or strategic response forces, we understandably protect that information from public release and falling into the hands of our adversaries -- as we expect they would do the same."

He pledged the Pentagon would continue to release near-daily updates of total cases among troops, DOD civilian workers, military dependents and defense contractors, which officials with Esper's public affairs office have done for nearly three weeks. Those numbers have grown steadily with each release -- eclipsing 1,000 cases in Monday's announcement.

As of Monday morning, the Pentagon reported 633 service members were among 1,087 total cases within the Defense Department community. Among those troops, 64 had recovered by Monday, while 26 were hospitalized. The latest data shows a dramatic increase in cases among troops since Friday, when the Pentagon reported 343 cases among service members.

The individual military services remain authorized to report coronavirus cases within their ranks to the public, Hoffman said.

"While services will not release the numbers of cases at each base, we will continue to work closely with the local communities to ensure the health and well-being of all," he said. "Individual installations [and] commands will continue to work closely with their respective community's health agencies on reporting, as ultimately our bases are part of a larger civilian community."

The mayor of San Antonio, Texas, Ron Nirenberg, objected to Esper's decision.

"I think this is a global pandemic, and the public has a right to know," he said in an interview Monday with the San Antonio Express-News.

"The lack of information is complicating a coordinated pandemic response at the state and federal level," said the mayor, whose city has four major military installations in the area.

He added that "one of the biggest battles that we have is helping people understand the seriousness of the situation."

The policy change came after Esper hinted last week during an interview with the Reuters news agency that he would soon begin withholding "disaggregated numbers" related to the virus. But the defense secretary did not specify what information would be withheld, Reuters reported.

On Sunday, Army officials in Stuttgart, Germany, announced they could no longer provide the public updated information about cases in their local area. At that time, Stuttgart, which houses headquarters for U.S. European Command and U.S. Africa Command, had reported at least 80 infections among its personnel.

Meanwhile, officials at Camp Humphreys in South Korea on Monday confirmed a fifth case of the virus among personnel assigned to that base, the largest U.S. base in that country. It was not immediately clear why that information was released to the public given the new policy.

Defense officials at several stateside military posts confirmed Monday that they had been issued the order to stop providing data about their cases. Several of these officials raised concerns that the new ban on local data could harm their ability to inform their own force and strain their ability to work with officials in their surrounding civilian communities amid the pandemic. The officials spoke on condition of anonymity to speak about the policy.

"We'll have to work through it," one of the officials said. "People are not going to be happy. I don't think they're going to understand this."

Individual installations had been providing the number of cases via official news releases, statements on their websites and largely through social media, including hosting virtual town hall events, in which top commanders provided updates on the conditions on their bases and answered questions from the public.

Hoffman said the Defense Department would not conceal information about coronavirus-related deaths on its installations and would work to keep local officials abreast of any "health threats" coming from military bases.

"We appreciate our citizens understanding as we protect operational security and our nation's readiness," he said.

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