The new coronavirus typically spreads via droplets when an infected person coughs or sneezes. The droplets carry viral particles and can land on someone else's nose or mouth or get inhaled.
But a person could potentially get the coronavirus if they touch a surface or object that has viral particles on it and then touch their mouth, nose, or eyes. The lifespan of the virus on a given surface depends on myriad factors, including the surrounding temperature, humidity, and type of surface.
A study published April 2 in the journal The Lancet Microbe revealed how long the COVID-19 virus lasts on various common surfaces. The authors found that the virus lasted longest — seven days — on the outer layer of surgical masks.
How long the coronavirus can survive on surfaces
The researchers behind the new study tested the virus' life span in a 71-degree-Fahrenheit room at 65% relative humidity. After three hours, the virus had disappeared from printing and tissue paper. It took two days for it to leave wood and cloth fabric. After four days, it was no longer detectable on glass or paper money. It lasted the longest, seven days, on stainless steel and plastic.
Strikingly, the authors wrote, the coronavirus was still present on the outward-facing side of a surgical mask on day seven of the investigation. That's the longest duration of all the materials they tested.
The study followed earlier research that also measured the coronavirus' lifespan on a range of household surfaces. The prior study, published March 17 in the New England Journal of Medicine, suggested the virus could live up to four hours on copper and up to a day on cardboard. The researchers found that the virus lasted up to three days on plastic and stainless steel — a shorter time than the results in the the Lancet study.
The researchers also compared the new coronavirus' life span on surfaces with that of the SARS coronavirus. In a 70-degree Fahrenheit room at 40% relative humidity, they found that both coronaviruses lived the longest on stainless steel and polypropylene, a type of plastic used in everything from food-storage containers to toys. Both viruses lasted up to three days on plastic, and the new coronavirus lasted up to three days on steel.
On cardboard, however, the new coronavirus lasted three times longer than SARS did: 24 hours, compared with eight hours.
Temperature and humidity play a role in how long the virus survives
Some coronaviruses, including this new one, have a viral envelope: a fat layer that protects viral particles when they travel from person to person in the air. That sheath can dry out, however, killing the virus. Temperature and humidity affect that process.
One recent study found that an 18-degree Fahrenheit jump, from 68 degrees to 86 degrees, decreased how long SARS lasted on steel surfaces by at least half.
The new Lancet study found a similar link between the virus' lifespan and the surrounding temperature. At 4 degrees Celsius (39 degrees Fahrenheit), the virus lasted up to two weeks in a test tube. When the temperature was turned up to 37 degrees Celsius (99 degrees Fahrenheit), its lifespan dropped to one day.
Some research has also suggested that increases in relative humidity reduce how readily the virus can spread between people.
You're unlikely to get the coronavirus from your mail
Even though the coronavirus can survive for a day on cardboard, it's unlikely that anyone would contract it after touching a box that arrives in the mail.
That's because shipping conditions make it difficult for the coronavirus to survive.
"Viruses are likely to only live a few hours to a few days under the sort of conditions we expose packages to, including shifts in temperature and humidity," Rachel Graham, an epidemiologist at the University of North Carolina, previously told Business Insider.
The Centers for Disease Control and Prevention says "there is likely very low risk of spread from products or packaging that are shipped over a period of days or weeks at ambient temperatures."
If you're concerned about your packages, though, Graham suggests using surface disinfectants like Lysol or bleach. These can kill viral particles within 15 seconds, but if you want to be extra careful, you can wait five to six minutes, she said.
But the precaution is likely unnecessary.
"If we had transmission via packages, we would have seen immediate global spread out of China early in the outbreak," Elizabeth McGraw, the director of the Center for Infectious Disease Dynamics at Pennsylvania State University, previously told Business Insider.
"We did not see that, and therefore I think the risk is incredibly low," she added.
