They are “petri dishes for bacteria and carriers of harmful pathogens,” read one warning from a plastics industry group. They are “virus-laden.”

The group’s target? The reusable shopping bags that countless of Americans increasingly use instead of disposable plastic bags.

The plastic bag industry, battered by a wave of bans nationwide, is using the coronavirus crisis to try to block laws prohibiting single-use plastic. “We simply don’t want millions of Americans bringing germ-filled reusable bags into retail establishments putting the public and workers at risk,” an industry campaign that goes by the name Bag the Ban warned Tuesday, quoting a Boston Herald column outlining some of the group’s talking points.

The Plastics Industry Association is also lobbying to quash plastic bag bans. Last week, it sent a letter to the U.S. Department of Health and Human Services requesting that the department publicly declare that banning single-use plastics during a pandemic is a health threat.

“We ask that the department speak out against bans on these products as a public safety risk,” the industry group wrote. It said the agency should “help stop the rush to ban these products by environmentalists and elected officials that puts consumers and workers at risk.”

The science around reusable bags and their potential to spread disease is contentious. An oft-cited study by researchers at the University of Arizona and Loma Linda University found that reusable plastic bags can contain bacteria and that users don’t wash reusable bags very often. The study was funded, however, by the American Chemistry Council, which represents major plastics and chemicals manufacturers. The study recommends that shoppers simply wash their reusable bags, not replace them.

Another episode cited by the plastics groups is based on a news article about a traveling girls’ soccer team that came down with the norovirus after one of the athletes spread the virus to her teammates. The surface of a reusable grocery bag in their hotel room tested positive for the virus.

Environmental experts stress that single-use plastics can still harbor viruses and bacteria they pick up from their manufacturing, transport, stocking or use. A study by the U.S. National Institutes of Health found that the novel coronavirus can remain on plastics and stainless steel surfaces for up to three days and on cardboard for up to one day. Still, simply disposing of the bag would be safer in that case, according to proponents of single-use plastic.

What is clear, however, is that single-use plastic bans have become a growing threat for the plastics industry. Packaging, including single-use packaging, makes up around a third of end-use demand for plastic resins as a whole, according to the American Chemistry Council. Before the coronavirus outbreak, the nationwide move to ban plastic bags had reached California, Hawaii, New York, as well as cities like Boston; Boulder, Colorado; Chicago; Los Angeles; San Francisco; and Seattle.

Even before the virus outbreak, an industry-funded group had worked with local lawmakers to block local actions to reduce plastic, proposing model legislation designed to preempt bans on disposable bags, boxes, cups, and bottles in the name of protecting businesses and consumer choice.

But now disposability, once a dirty word, has become a selling point as hygiene takes priority over sustainability. Starbucks and Dunkin have suspended accepting refillable mugs because of concerns over transmission. And bottled water, disposable plastic gloves, masks and other plastic products are flying off store shelves.

Delays in plastic bag bans are already afoot. Last week, lawmakers in Maine voted to push back the state’s plastic bag ban until next year as part of a package of emergency coronavirus measures. Gov. Chris Sununu of New Hampshire issued an emergency health order requiring stores to use single-use paper or plastic shopping bags to prevent new infections. On Wednesday, Gov. Charlie Baker of Massachusetts temporarily banned the use of reusable shopping bags and mandated that stores do not charge for plastic or paper bags.

In New York, John Flanagan, the top Republican in the state Senate, called for the state this month to suspend the plastic bag ban that went into force March 1. The ban’s enforcement had already been delayed pending a legal challenge unrelated to the virus.

Some supermarket chains have moved ahead with their own ban on reusable bags. Midwestern supermarket chain Hy-Vee has said it was no longer accepting reusable bags at their stores. Price Chopper said on Twitter that it was phasing plastic bags back into use at its stores in New York.

Findings published this month by research company BloombergNEF predicted that concerns around food hygiene could increase plastic packaging use overall, “undoing some of the early progress made by companies” in reducing plastic waste.

But longer-term effects on industry depend on whether the move to delay plastic bag bans turns more permanent, said Julia Attwood, head of advanced materials at BloombergNEF. “I think if this is seen as a limited emergency measure, then there won’t be much of an effect on the long-term demand for plastic,” she said.

But other market factors are at play, she said. Because plastic is made from fossil fuels, plastic prices track oil prices — which have slumped. That has made recycling plastic less economical.

Meanwhile, “the alternatives aren’t ready, and people are suddenly much more concerned about hygiene than they are about the potential impact on the environment of plastics,” she said. “We’re in a little bit of a perfect storm.”