New York(CNN Business) Dozens of grocery store workers have died from the coronavirus, despite masks, temperature checks and capacity restrictions to keep them safe. So far, supermarkets have resisted the most draconian policy: banning customers from coming inside.

However, some worker experts, union leaders and small grocery owners believe it has become too dangerous to let customers browse aisles, coming into close range with workers. Grocery stores are still flooded with customers, and experts say it's time for large chains to go "dark" to the public and convert to curbside pickup and home delivery for food and other essential goods.

"Careless customers" are "probably the biggest threat" to workers right now, according to Marc Perrone, president of the United Food and Commercial Workers' union. The union said 85% of its grocery store member workers reported that customers are not practicing social distancing in stores.

"Anything that reduces the need for interaction with the public and allows for greater physical distancing will ultimately better protect grocery workers," said John Logan, professor and director of Labor and Employment Studies at San Francisco State University. "Shuttering stores and repurposing them for pickup and delivery only would be a positive step."

Many small, independent grocery stores have done this to protect their staff.

Mike Houston, general manager of Takoma Park Silver Spring Co-op in Takoma Park, Maryland, decided to close his grocery store to the public in late March, when the state announced a shelter-in-place order, and switch to curbside pickup.

"It was clearer that there was no real way to protect my staff and the public, especially as we served 960 people a day on average in a 4,200-square-foot store," Houston said. "I'm unwilling to put grocery store employees, essential though we are, in a position to risk what can be a fatal infection."

Some large companies like Best Buy (BBY), which has a strong online infrastructure, have also switched over to this model during the crisis.

New regulations

Public safety officials are not requiring essential stores to shut down to customers, but the US Labor Department last week recommended that retailers start "using a drive-through window or offering curbside pick-up" to protect workers from exposure to coronavirus. The California Department of Industrial Relations said this week that companies should "encourage customer use of online order and pickup."

Some big grocers are slowly starting to move in this direction. Whole Foods has closed down a store in New York City's Bryant Park area and transitioned it into an online-only store, focused solely on deliveries. Kroger (KR) and Giant Eagle have switched a few stores to pickup and delivery-only locations.

But these are a fraction of stores in their wide networks. And most large chains have hesitated to shut down to the public. Instead, they are implementing more limited policies like taking workers' temperatures and restricting the number customers inside stores at a time. Companies are calling on families to cut back on their trips to the store and shop alone if they can.

City and state governments are stepping in to force stricter safety measures than the companies have adopted. Los Angeles, Miami, Washington DC, New Jersey, Maryland and New York have ordered shoppers to wear masks or face coverings in stores. Vermont has required big box chains like Walmart to close down their "non-essential" sections like furniture, home and garden equipment and arts and crafts.

Will pickup and delivery-only work?

Some companies and safety experts say it's not feasible to convert all grocery stores to delivery and pickup-only outposts. Ordering systems for both pickup and delivery are completely overwhelmed by a crush of demand from customers in many areas of the country.

"We have no choice. They have to stay open. [America's grocery] delivery system has not matured to the point where we can switch to an entirely remote system," said Seth Harris, former deputy secretary of labor during the Obama administration.

Online pickup and delivery requires a much larger staff than grocery stores are currently equipped with. That could fill supermarkets to capacity with workers, defeating the purpose of removing the public from stores.

Paying that many workers would also cost grocers a lot more money, and many smaller chains don't have the resources. They have already hired more workers during the pandemic to meet demand, and they're raising pay for existing employees to convince them to stay on the job. Grocers operate on razor-thin margins, and for many, the recent increase in sales because of coronavirus has been wiped out by the increases they've needed to make in payroll.

"I think that's one of the major reasons chains are reluctant to do the switch," said Logan from San Francisco State University.

The inside of the Takoma Park Silver Spring Co-op in Takoma Park, Maryland. The store has closed down to customers and converted to solely online orders.

A Trader Joe's representative said that while "we understand that during this time customers would appreciate a delivery or pick up service," the grocer's "systems are not set up in a way that would allow us to be able to offer these services, and at the same time maintain our commitment to offering value to our customers."

Switching to online pickup and delivery may also burden low-income customers who can't afford fees that often come with these orders, customers without internet access and food stamp recipients. Most food stamp recipients are ineligible to use their assistance to purchase groceries online, although the Department of Agriculture has doubled the number of states that allow food recipients to order online in the past few weeks.

And converting to online-only may not completely solve the safety problem either because an influx of gig workers would have to be in the store to pick and fulfill all of the orders.

It's an imperfect solution, said Charlane Obernauer, executive director of the New York Committee for Occupational Safety and Health. "Workers would still have exposure if they are delivering goods or if they are in the supermarket."

Still, in Malvern, Iowa, Mulholland Grocery has stopped allowing customers inside and moved to curbside pickup.

"We're in a small town. The employees that I have, they're just like family. I have known many of these people my whole life. I don't want to take the chance of having someone get sick," said owner Tom Mulholland. "There are very few businesses that get the foot traffic that a grocery store does."

Mulholland and Mike Houston in Maryland say their staffs are working harder than ever to select all of their customers' orders, but they're getting more efficient each day and the trade-off is worth it to keep everyone safe.

"Any store still allowing hundreds of members of the public to enter every day is taking a calculated risk on behalf of their front line staff," Houston said. "That is highly irresponsible to me."