Walmart and Sam's Club will require all employees to wear masks or other face coverings starting Monday to prevent the spread of the coronavirus.

Shoppers also will be encouraged to wear face masks as part of the retailers' updated COVID-19 response.

The retail giant announced the changes in a letter sent to employees that was posted on Walmart.com late Friday.

The employee policy is for U.S. stores, clubs, distribution and fulfillment centers, and corporate offices, according to the letter written by Walmart U.S. president and CEO John Furner and Sam's Club CEO Kath McLay.

"We have evolved our policy on face coverings from optional to mandatory as public health guidance has shifted," the letter said. "The CDC now recommends wearing face coverings in public settings, including grocery stores, to help curb the spread of the virus."

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Employees can bring their own masks if they meet certain guidelines or the retailers say they will provide them after employees pass the daily health screens and temperature checks, which were first announced March 31.

In early April, health and government officials updated recommendations on face coverings and started asking all people to wear cloth masks in public places like grocery stores and pharmacies.

A growing number of states, towns and cities took the recommendations further and are requiring consumers to wear masks in stores and other businesses.

"Although most state and local governments do not mandate the use of face coverings in public settings, the CDC has reported that recent studies show a significant portion of individuals with the virus lack symptoms and can transmit the virus," the CEOs said in the letter. "With this knowledge, we believe it is simply in everyone’s best interest to use masks or face coverings to curb the spread of this disease."

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