Like many respiratory viruses, Covid-19 spreads in tiny droplets released from the nose and mouth of an infected person as they cough.
One cough produces up to 3,000 droplets which can land on other people, clothing and surfaces, smaller particles can remain in the air. Each droplet contains tens of thousands of copies of the virus.
The virus is shed in feces, so anyone not washing their hands can contaminate everything they touch.
Some studies on other coronaviruses found they can survive on metal, glass, and plastic for as long as nine days unless properly disinfected. Some can even hang around for up to 28 days in low temperatures.
US National Institutes of Health (NIH) virologists have done some of the first tests of how long SARS-CoV-2 can last for on different surfaces. The study shows that the virus could survive in droplets for up to three hours after being coughed out.
The NIH study found that the virus survives for longer on cardboard – up to 24 hours – and up to 2-3 days on plastic and stainless-steel surfaces.
On clothing and other surfaces harder to disinfect, it is not yet clear how long the virus can survive. Although they still do test it on clothing, the absorbent natural fibers may cause the virus to dry up quickly.
“We speculate due to the porous material, it desiccates rapidly and might be stuck to the fibers.” Changes in temperature and humidity may also affect how long it can survive, and so may explain why it was less stable in suspended droplets in the air, as they are more exposed.
The ability of the virus to linger for so long only underlines the importance of hand hygiene and cleaning of surfaces.