From the moment coronavirus reached UK shores, public health advice stressed the importance of washing hands and deep-cleaning surfaces to reduce the risk of becoming infected.
The advice was informed by mountains of research into the transmission of other respiratory viruses: it was the best scientists could do with such a new pathogen.
But as the pandemic spread and data rolled in, some scientists began to question whether the focus on hand hygiene was as crucial as it seemed. Contaminated surfaces, such as doorknobs and light switches – “fomites”, to use the scientific terminology – may not be such a big deal, they claimed.
The issue has resurfaced after Monica Gandhi, a professor of medicine at the University of California, San Francisco, told the US science magazine Nautilus that the easiest way to catch the virus was through droplets and aerosols sprayed from an infected person’s mouth or nose.
“It’s not through surfaces,” she said. “We now know the root of the spread is not from touching surfaces and touching your eye. It’s from being close to someone spewing virus from their nose and mouth, without in most cases knowing they are doing so.”
Gandhi’s is not a lone voice. Her comments follow a prominent paper in the Lancet from Emanuel Goldman, a professor of microbiology at Rutgers University in New Jersey. He was sceptical about the relevance of scientific studies that showed the virus could survive on surfaces for days at a time.
“In my opinion,” he wrote, “the chance of transmission through inanimate surfaces is very small, and only in instances where an infected person coughs or sneezes on the surface, and someone else touches that surface soon after the cough or sneeze.” He defined soon as within one to two hours.
Dr Julian Tang, an honorary associate professor of respiratory sciences at the University of Leicester, thinks hand washing should stay but agrees the risk from fomites has been overplayed.
He points to documents from the UK government’s Scientific Advisory Group for Emergencies (Sage) that estimate hand washing can reduce acute respiratory infections by only 16%. Meanwhile, he adds, the World Health Organization has warned about surfaces being a likely route of transmission while conceding there are no reports demonstrating infection this way.
Tang believes that a preoccupation with contaminated surfaces distracted countries from taking airborne transmission seriously and played down the necessity of wearing masks. “What we’ve always said is that the virus transmits by all routes. There might be some transmission by hand and fomites and we’re not opposed to hand washing, but the emphasis is wrong,” he told the Guardian.
“A lot of money has been spent, and time has been spent, deep-cleaning surfaces, when the main risk is probably people talking to each other,” he said. “If we had put that investment into masks earlier on, if we had put all the effort on hand washing and deep-cleaning into universal mask-wearing early on, we’d almost certainly not have such a massive epidemic in Europe and North America.”
Goldman’s argument was founded on studies that showed traces of virus lingering on surfaces were not “viably” infectious. But William Keevil, a professor of environmental healthcare at the University of Southampton, is not impressed. Hospital surfaces should be regularly disinfected, he points out, so it is hardly surprising that any virus lingering there is not infectious. “We have been investigating disinfectants with residual activity for surface cleaning and they can work well,” he said.
Work by Keevil and others has shown that the Sars-CoV-2 virus can remain infectious on hard surfaces for days. What constitutes “viable” is still unclear, however, and will vary depending on whether the virus enters the eyes, nose or mouth through large droplets or tiny aerosols, or by touching those areas with contaminated hands. Another complicating factor is the person themselves – different people will have different susceptibilities to the virus. “Even low numbers of virus could be infectious to susceptible people,” he said.
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