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Waffle House has declared a "Waffle House Index Red," as the chain closes more than fifth of its restaurants in response to the coronavirus pandemic.

The Georgia-based chain's approximately 2,000 restaurants are usually open 24 hours, seven days a week, 365 days a year. Now, 418 locations are closed, a Waffle House Facebook post said Wednesday. Waffle House had originally closed 365 stores on Tuesday.

"#WaffleHouseIndexRed," said the posts.

The Waffle House Index, which was coined nearly a decade ago, refers to the measure of destruction caused by a natural disaster based on how many Waffle Houses remain open or have closed. The chain, which has restaurants in about two dozen states but is a staple in the South, is known for its disaster preparedness and ability to stay open during destructive weather events, like tornadoes and hurricanes.

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A former FEMA director said the agency monitors the closures of Waffle Houses following natural disasters to determine where to focus their response.

"If you get there and the Waffle House is closed?" former-FEMA Administrator Craig Fugate said, according to The Wall Street Journal. "That's really bad. That's where you go to work."

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An index yellow means Waffle Houses in a certain location are serving a limited menu, due to low food supplies and no power or power only from a generator.

The chain, which was established in 1955, announced on March 15 that all its restaurants were open. "At Waffle House, we take great pride in being open to serve the communities where we work, live and raise our families," the company said in a statement. "Our mission has been to provide an essential service in our communities during difficult times for all, including first responders and health care providers."

The statement said Waffle House was also focused on keeping its nearly 45,000 employees working. The chain had increased cleaning and sanitization in its stores.

By March 18, some Waffle Houses had transitioned to serving to-go orders only. "Our associates are the true heroes during this time and appreciate any order you are able place with them!" said a Waffle House Facebook post that day.

Waffle House did not immediately respond to a request for comment Wednesday.