COVID-19 rarely spreads through surfaces.
“We don’t have a single documented case of covid-19 transmission from surfaces. Not one.” According to researchers at these three institutions.
Joseph G. Allen is an associate professor and director of the Healthy Buildings program at Harvard University’s T.H. Chan School of Public Health. Charles Haas is a professor of environmental engineering at Drexel University. Linsey C. Marr is a professor of civil and environmental engineering at Virginia Tech.
COVID-19 is caused by the SARS-CoV-2 virus, which spreads between people, mainly when an infected person is in close contact (less than 1 metre apart or 3 feet) with another person.
The virus can spread from an infected person’s mouth or nose in small liquid particles when they cough, sneeze, speak, sing or breathe heavily. These liquid particles are different sizes, ranging from larger ‘respiratory droplets’ to smaller ‘aerosols’.
Other people can catch COVID-19 when the virus gets into their mouth, nose or eyes, which is more likely to happen when people are in direct or close contact (less than 1 metre apart) with an infected person.
Current evidence suggests that the main way the virus spreads is by respiratory droplets among people who are in close contact with each other.
Aerosol transmission can occur in specific settings, particularly in indoor, crowded and inadequately ventilated spaces,
CDC updates COVID-19 transmission webpage to clarify information about types of spread
Media Statement For Immediate Release: Friday, May 22, 2020
The primary and most important mode of transmission for COVID-19 is through close contact from person-to-person. Based on data from lab studies on COVID-19 and what we know about similar respiratory diseases, it may be possible that a person can get COVID-19 by touching a surface or object that has the virus on it and then touching their own mouth, nose, or possibly their eyes, but this isn’t thought to be the main way the virus spreads.
Only a handful of studies have looked for viable virus outside the lab. Tal Brosh-Nissimov, who heads the infectious-diseases unit at the Assuta Ashdod University Hospital in Israel, and his colleagues swabbed personal items and furniture in hospital isolation units and rooms at a quarantine hotel. Half of the samples from two hospitals and more than one-third of samples from the quarantine hotel were positive for viral RNA. But none of the viral material was actually able to infect cells, the researchers reported.
Ben-Shmuel, A. et al. Clin. Microbiol. Infect. 26, 1658–1662 (2020).
Estimates of transmission based on levels of viral RNA persisting in the environment seem to bear this out. From April to June, environmental engineer Amy Pickering then at Tufts University in Medford, Massachusetts, and her colleagues took weekly swabs of indoor and outdoor surfaces around a town in Massachusetts. On the basis of the levels of RNA contamination and how often people touched surfaces such as doorknobs and buttons at pedestrian crossings, the team estimated that the risk of infection from touching a contaminated surface is less than 5 in 10,000 — lower than estimates for SARS-CoV-2 infection through aerosols, and lower than surface-transmission risk for influenza or norovirus. Harvey, A. P. et al. Environ. Sci. Technol. Lett. https://doi.org/10.1021/acs.estlett.0c00875 (2020).
Hundreds of studies of COVID-19 transmission have been published since the pandemic began, yet there is thought to be only one that reports transmission through a contaminated surface, by what it termed the snot–oral route. According to the report, a person with COVID-19 in China blew his nose with his hand and then pressed a button in his apartment building elevator. A second resident in the building then touched the same button and flossed with a toothpick immediately after, thereby transferring the virus from button to mouth. But without genome sequences of the viruses infecting each person, transmission through another unknown person couldn’t be ruled out.
Xie, C. et al. BMC Public Health 20, 1202 (2020)
But Emanuel Goldman, a microbiologist at Rutgers New Jersey Medical School in Newark, decided to take a closer look at the evidence around fomites. What he found was that there was little to support the idea that SARS-CoV-2 passes from one person to another through contaminated surfaces. He wrote a pointed commentary for The Lancet Infectious Diseases in July, arguing that surfaces presented relatively little risk of transmitting the virus. His conviction has only strengthened since then, and Goldman has long since abandoned the gloves.
Goldman, E. Lancet Infect. Dis. 20, 892–893 (2020).
Experts say that it makes sense to recommend hand washing, but some researchers are pushing back against the focus on surfaces. In December, engineer Linsey Marr at Virginia Tech in Blacksburg co-wrote an opinion article for The Washington Post imploring people to ease up on cleaning efforts. “It’s become clear that transmission by inhalation of aerosols — the microscopic droplets — is an important if not dominant mode of transmission,” says Marr, who studies airborne disease transmission. Excessive attention on making surfaces pristine takes up limited time and resources that would be better spent on ventilation or the decontamination of the air that people breathe, she says.