Shoppers must wear a face covering or mask to be allowed in Costco stores starting Monday to prevent the spread of COVID-19. All members, guests and employees must comply, the company said.

Members who don’t have a mask with them will be supplied a free one for the first week only.

Costco is the first major national retailer to mandate mask wearing by customers, although local and regional retailers have also done so.

The requirement does not apply to children under the age of 2 or to individuals who are unable to wear a mask or face covering due to a medical condition, according to Costco’s website.

On Twitter, members and nonmembers wasted no time offering up brickbats and bouquets. “I will not comply with face masks and will not shop at #costco. Bye #costco!” wrote @Glitzstyle. Others such as @PCEHorvath responded, “This is a very serious situation and wearing a mask is the responsible thing to do — for you and those you encounter. Bravo #Costco.”

Major Twin Cities retailers have not yet mandated masks for all, including Target, but others in the country have started mask requirements, including Martin’s Super Markets in Indiana and Michigan. JetBlue airlines requires its customers to wear masks from the passenger gate to deplaning.

Seven states — Connecticut, Hawaii, Maryland, New Jersey, New York, Pennsylvania, and Rhode Island — have mandated masks in public places as have some cities such as Birmingham, Ala., and several cities in Massachusetts and Texas.

“Costco is leaning on government regulations to do this a little ahead of the curve,” said George John, professor of marketing at the University of Minnesota’s Carlson School of Management. “It will play well to their older, somewhat affluent base but some large families may say, ‘I can’t put masks on my kids.’ ”

In other changes effective Monday, Costco’s stores and gas stations will return to regular hours in Minnesota and most other locations, although it is still allowing only one or two people per membership card to enter. Members with a disability or those over the age of 60 will be able to shop from 9 to 10 a.m. weekdays, instead of Tuesdays, Wednesdays and Thursdays.