In response to the global coronavirus threat, Apple will temporarily close hundreds of stores in more than 20 countries to protect the health of both employees and customers.

It’s the largest such move by a retailer since the crisis began.

CEO Tim Cook made the announcement just before midnight PDT Friday, tweeting: “In our workplaces and communities, we must do all we can to prevent the spread of COVID-19. Apple will be temporarily closing all stores outside of Greater China until March 27 and committing $15M to help with worldwide recovery.”

He said Apple stores in China that had been closed during the early outbreak there will now be reopening.

The company remains committed to “providing exceptional service to our customers” via online sales and support services. Customers who want to purchase Apple products can go to www.apple.com or download the Apple Store app, he said. Those who need help troubleshooting issues with their products should visit support.apple.com.

The Cupertino-based tech giant’s largest concentration of stores is in its home state of California, which has 53. Globally, there are stores from Australia to the United Arab Emirates.

Cook opened his statement with a thank you to Apple employees and suppliers in China, which is one of Apple’s biggest markets both for selling its products and making devices like iPhones and iPads.

“Though the rate of infections has dramatically declined, we know COVID-19’s effects are still being strongly felt,” he wrote. “I want to express my deep gratitude to our team in China for their determination and spirit. As of today, all of our stores in Greater China have reopened. I also want to thank our operations team and partners for their remarkable efforts to restore our supply chain. What we’ve learned together has helped us all develop the best practices that are assisting enormously in our global response.”

Those practices, he said, provided the impetus for putting the retail stores on hiatus. “One of those lessons is that the most effective way to minimize risk of the virus’s transmission is to reduce density and maximize social distance. As rates of new infections continue to grow in other places, we’re taking additional steps to protect our team members and customers.”

During the shutdown, Cook added, “All of our hourly workers will continue to receive pay in alignment with business as usual operations.”

Apple’s other leave policies have been expanded to assist employees recovering from illness themselves, caring for sick relatives, facing mandatory quarantine or dealing with child care challenges created by school closures.

The amount the company has pledged for relief has now reached $15 million, Cook said. Those monies are earmarked to “help treat those who are sick and to help lessen the economic and community impacts of the pandemic.”

Any employee donations will be matched two-for-one.

Cook ended his announcement with a note of gratitude and a quote from the 16th president of the United States:

“There is no mistaking the challenge of this moment. The entire Apple family is indebted to the heroic first responders, doctors, nurses, researchers, public health experts and public servants globally who have given every ounce of their spirit to help the world meet this moment. We do not yet know with certainty when the greatest risk will be behind us.

“And yet I have been inspired by the humanity and determination I have seen from all corners of our global community. As President Lincoln said in a time of great adversity: ‘The occasion is piled high with difficulty, and we must rise with the occasion. As our case is new, so we must think anew, and act anew.’ ”