HONG KONG — At Hong Kong’s deserted airport, cleaning crews constantly spray baggage trolleys, elevator buttons and check-in counters with antimicrobial solutions. In New York City, workers continually disinfect surfaces on buses and subways. In London, many pubs spent lots of money on intensive surface cleaning to reopen after lockdown — before closing again in November.
All over the world, workers are soaping, wiping and fumigating surfaces with an urgent sense of purpose: to fight the coronavirus. But scientists increasingly say that there is little to no evidence that contaminated surfaces can spread the virus. In crowded indoor spaces like airports, they say, the virus that is exhaled by infected people and that lingers in the air is a much greater threat.
Hand washing with soap and water for 20 seconds — or sanitizer in the absence of soap — is still encouraged to stop the virus’s spread. But scrubbing surfaces does little to mitigate the virus threat indoors, experts say, and health officials are being urged to focus instead on improving ventilation and filtration of indoor air.
“In my opinion, a lot of time, energy and money is being wasted on surface disinfection and, more importantly, diverting attention and resources away from preventing airborne transmission,” said Dr. Kevin P. Fennelly, a respiratory infection specialist with the United States National Institutes of Health.
A false sense of security
Some experts suggest that Hong Kong, a crowded city of 7.5 million residents and a long history of infectious disease outbreaks, is a case study for the kind of operatic surface cleaning that gives ordinary people a false sense of security about the coronavirus.
The Hong Kong Airport Authority has used a phone-booth-like “full-body disinfection channel” to spritz airport staff members in quarantine areas. The booth — which the airport says is the first in the world and is being used in trials only on its staff — is part of an all-out effort to make the facility a “safe environment for all users.”
Such displays can be comforting to the public because they seem to show that local officials are taking the fight to Covid-19. But Shelly Miller, an expert on aerosols at the University of Colorado Boulder, said that the booth made no practical sense from an infection-control standpoint.
Viruses are emitted through activities that spray respiratory droplets — talking, breathing, yelling, coughing, singing and sneezing. And disinfecting sprays are often made from toxic chemicals that can significantly affect indoor air quality and human health, Dr. Miller said.
“I can’t understand why anyone would think that disinfecting a whole person would reduce the risk of transmitting virus,” she said.
A range of respiratory ailments, including the common cold and influenza, are caused by germs that can spread from contaminated surfaces. So when the coronavirus outbreak emerged last winter in the Chinese mainland, it seemed logical to assume that these so-called fomites were a primary means for the pathogen to spread.
Studies soon found that the virus seemed to survive on some surfaces, including plastic and steel, for up to three days. (Studies later showed that much of this is likely to be dead fragments of the virus that are not infectious.) The World Health Organization also emphasized surface transmission as a risk, and said that airborne spread was a concern only when health care workers were engaged in certain medical procedures that produce aerosols.
But scientific evidence was growing that the virus could stay aloft for hours in tiny droplets in stagnant air, infecting people as they inhaled — particularly in crowded indoor spaces with poor ventilation.
In July, an essay in The Lancet…