A question that has been concerning health agencies and scientists over the last few months is how long SARS-CoV-2, the pathogen that causes COVID-19, can survive in the air and on surfaces. Knowing this can make for better guidelines on how to stop the spread, which are currently based on results for SARS-CoV-1, the coronavirus responsible for the SARS pandemic in the early 2000s.
We know that the virus can be transmitted through droplets in the air (which is why you must cough and sneeze into a tissue and immediately throw them away, or your elbow) and touching contaminated surfaces (think door handles, shopping trolleys, handrails etc), which is why it's so important to implement physical distancing and wash your hands.
In a new study, published in The New England Journal of Medicine, researchers have tested the stability of the two viruses, ie how long they can survive on varying surfaces, in five environmental conditions found in everyday home or hospital settings: on plastic, stainless steel, copper, and cardboard, as well as how long they can remain infectious in the air suspended in aerosols.
The team found that the viruses were still detectable on copper up to four hours after being contaminated, and up to 24 hours on cardboard. Both viruses could still be detected on plastic and stainless steel up to two to three days later. This is broadly in line with previous research on other coronaviruses.
"This virus is quite transmissible through relatively casual contact, making this pathogen very hard to contain," co-author James Lloyd-Smith, a UCLA professor of ecology and evolutionary biology, said in a statement. "If you're touching items that someone else has recently handled, be aware they could be contaminated and wash your hands."
The researchers also looked at suspension of the pathogen in the air by producing contaminated aerosols. They found that under those conditions the virus remains airborne and detectable for up to three hours. While this might seem like an alarming finding, experts not involved in the study stress how nebulization – a drug delivery device used to administer medication in the form of a mist inhaled into the lungs – is not an ideal way to simulate how humans spread the virus.
“The authors used a nebulizer to generate aerosols of the virus. However, COVID-19 is primarily a droplet spread infection, so aerosols are not a particularly valid model of transmission,” Paul Hunter, Professor in Medicine at the University of East Anglia, said.
“Droplets fall out of the air quite quickly compared to aerosols and so the risk remains from standing within about a meter or so of a case or from touching those surfaces onto which such droplets have settled. The advice remains not to get too close to possible cases and wash your hands regularly, especially after touching surfaces before touching your own face.”
Avoiding touching surfaces and our faces is not easy, but it's important to remain vigilant in maintaining good hygiene, washing hands regularly, when out use alcohol hand sanitizer, wipe down surfaces with disinfectant regularly, and if you need to leave home maintain a physical distance of at least 1.5 meters from others.