Tests show coronavirus droplets released when someone coughs/sneezes remain infectious as aerosol for at least 3 hrs. On plastic/stainless steel surface still viable after 3 days; copper 4 hrs; cardboard about 24 hrs. But half life in each case is shorter
reuters.com/article/us-hea…
reuters.com/article/us-hea…
The survival/infection rates measure when any detectable particle is still infectious; but not all particles in a droplet stay infectious for these timeframes. Many die off so that only half or fewer remain infections for the entire timeframes mentioned.
Here's a better article about that study on how long coronavirus particles remain infections nytimes.com/2020/03/17/hea…
"The coronavirus can live for three days on some surfaces, like plastic and steel [but] experts say the risk of consumers getting infected from touching those materials is still low, ...
...the virus disintegrates over the course of a day on cardboard, lessening the worry among consumers that deliveries will spread the virus during this period of staying and working from home.
..[but] when the virus becomes suspended in droplets smaller than 5 micrometers—known as aerosols—it can stay suspended for about a half-hour...before drifting down and settling on surfaces where it can linger for hours" which could have implications for health-care workers
That the virus can stay infectious in aerosols contradicts what World Health Organization has said. "But in fact, it can travel through the air and stay suspended for that period of about a half-hour....
"The virus does not linger in the air at high enough levels to be a risk to most people who are not physically near an infected person. But the procedures health care workers use to care for infected patients are likely to generate aerosols...
..Health care workers might also collect those tiny droplets and larger ones on their protective gear when working w/ infected patients. They might resuspend these big and small droplets into the air when they take off this protective gear and become exposed to the virus then"
And here's a good thread explaining the difference between a droplet and aerosol particle and whether masks protect against the latter
