Michael Abrahams | How long can the new coronavirus survive outside the human body?
As COVID-19, caused by the virus SARS-CoV-2, a coronavirus, spreads across the world, many questions are being asked. One of the most commonly asked is: “How long can the virus survive outside the human body?”
The new coronavirus typically spreads via airborne droplets. For example, when an infected person coughs or sneezes, droplets containing the virus can land on someone else's nose or mouth or get inhaled, causing them to get infected and become ill. A single cough can produce up to 3,000 droplets, making transmission by this route relatively easy.
We also know that you can get the coronavirus if you touch a surface or object that has viral particles on it and then touch your mouth, nose, or eyes. There are therefore concerns about the life span of the virus on various surfaces.
Emerging research has found that the survival of the virus on different surfaces depends on several factors, including not only the type of surface, but also the surrounding temperature and humidity.
A study published earlier this month in the New England Journal of Medicine examined the survival of the virus on different surfaces. The tests were carried out in a 70-degree Fahrenheit room at 40 per cent relative humidity. The survival on various surfaces was as follows:
- Air – 3 hours
- Copper - 4 hours
- Cardboard – 24 hours
- Stainless steel – 2-3 days
- Polypropylene plastic – 3 days
To put these results in perspective, if you leave your office after an infected person sneezes on your desk on a Friday afternoon, and return to work on Monday morning, touch a plastic container on your desk, and then rub your nose, it is possible for you to become infected.
If a person carrying the virus, who practices poor hygiene, touches a plastic or metal spoon in the lunchroom at your workplace on a Friday evening, and on Monday morning you go and use that same spoon to eat cereal, without washing it, you can get infected.
The longevity of the virus on steel and plastic is important to appreciate, as these substances are utilized to make objects that are frequently touched and held. Door handles and knobs, rails along steps and ramps, rails and poles on public transportation, faucets, light switches, elevator and intercom buttons, parking lot passes, keypads on computers, ATM keypads and cell phone cases utilize these materials.
The survival time of the virus of 24 hours on cardboard means that if, for example, you order a product from Amazon, the virus is unlikely to be transmitted on the box from its place of origin. However, if persons who are infected handle the box while delivering it to you, it is possible for you to pick up the virus.
As for the contents of the box, temperature and humidity play a big role in how long the virus can survive, with increases in both causing a decrease in transmission risk. Changes in these parameters during shipping make it difficult for the coronavirus to survive the journey.
According to the Centers for Disease Control and Prevention, "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.”
Elizabeth McGraw, the director of the Center for Infectious Disease Dynamics at Pennsylvania State University, also makes a good point. During an interview with the Business Insider, she said, "If we had transmission via packages, we would have seen immediate global spread out of China early in the outbreak."
EASY TO KILL
Unfortunately, the study did not examine the lifespan of the virus on glass, and the duration of its survival on clothing is not yet known, but it is likely not able to survive for a long time on porous materials such as fabric.
The lifespan of the virus on currency notes is also not known, but it would be wise to always wash your hands properly after handling money.
Of concern is the finding that the virus can also live in the air for up to three hours. Fine droplets between 1-5 micrometres in size, about 30 times smaller than the width of a human hair, can remain airborne for several hours in still air.
The good news is that the virus can be a badass in your body, but outside of it you can kick its butt. It is easy to kill. Soap and water, rubbing alcohol, hydrogen peroxide, bleach, and a variety of Lysol and Clorox products, among others, will destroy the virus on inanimate surfaces.
Regularly touched objects and surfaces should be cleaned frequently with appropriate agents, and you should wash your hands properly with soap and water or use a hand sanitiser with at least 62 per cent alcohol after touching them.
Please keep safe.