Can you get coronavirus by opening your mail?

Mail delivery is one of the few normal daily routines that haven't been disrupted during the coronavirus outbreak.

It also poses an unexpected concern in the era of the pandemic: Is it safe to handle and open mail as usual?

The new coronavirus could be detected for up to 24 hours on cardboard, and up to two to three days on plastic and stainless steel, a recent study found. Researchers didn't examine how long the bug stayed active on paper.

Letter carriers may touch countless envelopes and mailboxes as they deliver mail. It's conceivable some could be doing it while infected.

In a ProPublica report published this week, two mail carriers told the outlet they'd been pressured to stay on their routes despite showing symptoms of COVID-19.

Ten letter carriers also told ProPublica they'd been given little or no hand sanitizer. All spoke on condition of anonymity.

Almost 40,000 people have signed a petition calling on the United States Postal Service to "take immediate action to ensure the safety and rights of its workers, as well as the safety of its customers" by granting emergency sick leave and hazard pay to employees, and making gloves, sanitizer spray and face masks available at all stations.

The United States Postal Service said there's currently no evidence COVID-19 is being spread through the mail, pointing to guidance from the Centers for Disease Control and Prevention, the World Health Organization and the Surgeon General.

As of Thursday, 13 of the more than 630,000 USPS employees have tested positive for COVID-19, said spokesman Dave Partenheimer. The agency did not specify whether any of them were letter carriers. These employees had either traveled internationally to countries with widespread disease or live in areas of the U.S. where there has been community spread of the virus.

"We are not aware of any employee who has contracted COVID-19 as a result of his or her work for the Postal Service," Partenheimer told TODAY in a statement.

"The United States Postal Service is closely monitoring the Coronavirus Disease 2019 (COVID-19) situation and continues to follow strategies and measures recommended by the Centers for Disease Control and Prevention and public health departments."

As part of that effort, the agency is sharing the CDC guidance to its workers via stand-up talks, employee news articles, messages on bulletin boards, videos and an intranet site within USPS workplaces, Partenheimer said.

Expert shares advice:

Dr. Joseph Vinetz, an infectious disease doctor at Yale Medicine in Connecticut, said people don't need to take any special precautions while opening mail.

"Letter carriers and mailboxes just don't seem to be the most important or even any relevant aspect of COVID-19 transmission," Vinetz told TODAY.

"But it's reasonable just to wash your hands several times a day — any time you're contacting something that comes in from outside your home."

He wasn't worried about the public handling letters, USPS parcels or Amazon packages as long as they kept up their hand hygiene. It's fine to clean your mailbox with an antibacterial wipe if you wish, but since mailboxes aren't touched by very many people, Vinetz wasn't concerned about the virus being transmitted that way.

But he bristled at advice from some experts to wear rubber gloves while opening their mailbox or their mail, calling it "harmful."

"This virus doesn't infect people through the skin; it only infects people through the respiratory tract. By wearing gloves, it gives people a false sense of security and, more importantly, it wastes resources," Vinetz said.

"I advise strongly against using gloves for routine daily life activities. It does not make any sense to me as an infectious disease doctor."

Just remember: Whenever you're outside a home-controlled environment or bring a delivery into your house, wash your hands regularly for 20 seconds with soap and water, or use a hand sanitizer if hand washing is not possible, Vinetz advised.

"Common-sense precautions prevail regardless whether it's mail or not," he said.