Kroger, ShopRite, Stop & Shop and Walmart are among the chains adding off-duty police and other third-party security services to help control panicky crowds and prevent frenzies over limited-inventory items.

Others, such as Roundy’s, have added sneeze guards to shields for cashier cashiers and encourage social distancing. Some supermarkets are adding special shopping hours for senior citizens, limiting the number of customers who can be in each store and marking the floors in their stores near checkout lines to serve as visual cues to facilitate social distancing. 

Meanwhile in Philadelphia, two supermarkets created shopping cart-sanitizing stations to clean grocery carts and hand baskets and reassure virus-wary shoppers.