A Walmart Health Ambassador stands by the entrance to a Walmart store in Plano, Texas, the United States, on July 20, 2020. The world's largest retailer Walmart has announced that Walmart and Sam's Club shoppers in the United States will be required to wear face coverings starting July 20. In addition to posting clear signs at the front of stores, Walmart has created the role of Health Ambassador and will station them near the entrance to remind those without a mask. (Photo by Dan Tian/Xinhua)

Customers wearing face masks enter a Walmart store in Plano, Texas, the United States, on July 20, 2020. The world's largest retailer Walmart has announced that Walmart and Sam's Club shoppers in the United States will be required to wear face coverings starting July 20. In addition to posting clear signs at the front of stores, Walmart has created the role of Health Ambassador and will station them near the entrance to remind those without a mask. (Photo by Dan Tian/Xinhua)

Customers wearing face masks enter a Walmart store in Plano, Texas, the United States, on July 20, 2020. The world's largest retailer Walmart has announced that Walmart and Sam's Club shoppers in the United States will be required to wear face coverings starting July 20. In addition to posting clear signs at the front of stores, Walmart has created the role of Health Ambassador and will station them near the entrance to remind those without a mask. (Photo by Dan Tian/Xinhua)

Customers wearing face masks enter a Walmart store in Plano, Texas, the United States, on July 20, 2020. The world's largest retailer Walmart has announced that Walmart and Sam's Club shoppers in the United States will be required to wear face coverings starting July 20. In addition to posting clear signs at the front of stores, Walmart has created the role of Health Ambassador and will station them near the entrance to remind those without a mask. (Photo by Dan Tian/Xinhua)

Customers wearing face masks enter a Walmart store in Plano, Texas, the United States, on July 20, 2020. The world's largest retailer Walmart has announced that Walmart and Sam's Club shoppers in the United States will be required to wear face coverings starting July 20. In addition to posting clear signs at the front of stores, Walmart has created the role of Health Ambassador and will station them near the entrance to remind those without a mask. (Photo by Dan Tian/Xinhua)