Fears of catching the coronavirus from contaminated surfaces have prompted many of us to spend the past few months wiping the grocery store, leaving packages unopened and stressful of hitting elevator buttons.
But what is the real risk of catching Covid-19 from a surface or a germinated object?
The issue has recently been of concern to people and there has been some confusion after the Centers for Disease Control and Prevention made changes to its website last week. Social media sites and some media have suggested that the agency had downgraded its warnings and that surface transmission was no longer a concern.
“Based on data from laboratory studies of Covid-19 and what we know about similar respiratory illnesses, it is possible that a person could contract Covid-19 by touching a surface or object infected with the virus , then touching his own mouth. , the nose or maybe their eyes, “the agency wrote. “But it is not believed to be the primary means of spreading the virus. “
Does this mean we can get coronavirus by touching a door handle? Catch a frisbee? Do you share a pan?
The answer, in theory, is yes, that’s why you have to wash your hands often and avoid touching your face. A number of studies on influenza, rhinovirus, coronavirus and other microbes have shown that respiratory illnesses, including the new coronavirus, can be spread by touching contaminated surfaces, especially in places like daycares , offices and hospitals.
“What they say is that high contact surfaces like railings and door handles, elevator buttons are not the main driver of infection in the United States,” said Erin Bromage, comparative immunologist and professor of biology at the University of Massachusetts, Dartmouth. “But it’s always a bad idea to touch your face. If someone with an infectious cough coughs your hand and shakes your hand and rubs your eyes – yes, you are infected. Someone drinks from a glass, and you take it near the rim and rub your eyes or mouth later, you get infected. ”
Here is how the fomite transmission works. An infected person coughs or sneezes on their hands. Some droplets can splash on a nearby surface or the person spreads germs by touching a tap or counter before washing their hands. Studies show that coronavirus can last up to three days on plastic and steel, but once it lands on a surface, the amount of viable virus begins to disintegrate within hours. This means that a droplet on a surface is much more contagious right after sneezing – not so much a few days later.
Then you need to come and touch the contaminated surface, catch enough viable virus on your hands, and then touch your eyes, nose, or mouth. If all is well for the virus, you will get sick.
“There is a long chain of events that should occur for someone to become infected through contact with groceries, mail, takeout containers or other surfaces,” said Julia Marcus, infectious disease epidemiologist and assistant professor in the Department of Population Medicine at Harvard Medical School. “The last step in this causal chain is to touch your eyes, nose or mouth with your contaminated hand, so the best way to make sure the chain is broken is to wash your hands. “
An epidemic associated with a shopping center in Wenzhou, China, may have been powered by a fomite transmission. In January, seven workers who shared a desk in a shopping center fell ill when one of their colleagues returned from Wuhan. The mall was closed and public health officials followed two dozen more sick people, including several women who had been shopping at the mall, as well as their friends. None of them had contacted the first sick employees. The researchers speculated that female toilets or shopping center elevators were responsible for the transmission.
Other studies have used invisible fluorescent tracers – fake germs that glow in black light – to track the spread of germs from surfaces. The results are troubling. In one series of experiments, 86 percent of workers were contaminated when spray or powder tracers were placed on commonly touched objects in an office. When tracking powder was placed on a bathroom faucet and an exit door handle, light residue was found on the employees’ hands, face, telephone and hair. From a shared phone, the plotter has spread to office surfaces, cups, keyboards, pens and doorknobs. A contaminated photocopier button added a trail of fluorescent fingerprints transferred to documents and IT equipment. And just 20 minutes after returning from the office, false germs were found on backpacks, keys and handbags, as well as doorknobs, light switches, counters and kitchen appliances.
A video touring the Internet shows how the black light experience works. The light germs are put on the hands of a single dinner buffet, but at the end of the meal, everyone at the table came into contact with the light germs. The video explains why scientists are discouraging food sharing during a viral outbreak.
But while these experiments show how germs can spread on surfaces, the microbe still has to survive long enough and at a dose large enough to make you sick. Eugene M. Chudnovsky, professor at the City University of New York, notes that surfaces are not a particularly effective means of viral transmission. With the flu, for example, it takes millions of copies of the flu virus to infect a person through surface contact by hand to the nose, but it only takes a few thousand copies to infect a person when the virus the flu disappears from the air directly into the lungs.
Dr. Chudnovsky, a theoretical physicist whose research has focused on the spread of airborne infection, said a similar pattern is probably true for the new coronavirus, but the exact numbers are not known.
“I believe that the C.D.C. he is right when he says that surface transmission is not dominant, “said Dr. Chudnovsky. “The surfaces frequently touched by large numbers of people, such as doorknobs, elevator buttons, etc., can play a more important role in the spread of infection than objects accidentally touched, such as packages of food delivered to your home. “
Ultimately, the best way to protect ourselves from the coronavirus – whether surface transmission or close human contact – is always social distance, washing our hands, not touching our faces, and wearing masks.
“Hand washing is important not only for fomite transmission, but also for person-to-person transmission,” said Dr Daniel Winetsky, postdoctoral fellow in the division of infectious diseases at Columbia University. “The respiratory droplets we produce when speaking, coughing and sneezing fall mainly on our hands, and can fall on other people’s hands if they are within six feet of us. “