Workers in protective suits disinfect an area outside a barricaded community that was locked down for health monitoring after recent cases of Covid-19 were found in the area on March 28, in Beijing, China.

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Hong Kong CNN  — 

Hazmat suit-clad workers spraying clouds of disinfectant over city streets, building fronts, park benches and even parcels have become a common sight in pandemic-era China.

In Shanghai, the epicenter of the country’s largest outbreak, state media report that thousands of workers have been organized into teams to disinfect areas, with a focus on those known to have hosted Covid patients – a move the government sees as key to curbing the spread of the Omicron variant.

But the practice often extends much further. Seemingly any outdoor area is at risk of being targeted by workers wielding leaf-blower-style disinfectant machines, as China’s rigorous “zero-Covid” policy drives an obsession with sanitizing everything.

In Shanghai, fire fighters have been plucked from their duties to take up roles as disinfectors, a local youth league has recruited volunteers for disinfection squads, and emergency rescue teams from far-flung parts of China have been enlisted in the drive – often strapping on heavy equipment and full hazmat.

In some Shanghai neighborhoods, special chemical producing stations have been set up, while in others vehicles have been outfitted with chemical tanks and cannon-like devices to shoot disinfectant onto the streets, according to local media. Disinfection robots have been stationed at railway stations, and have been set up to patrol some quarantine centers.

But these efforts – and others, like the insistence that workers wear hazmat suits and the blaring, recorded messages playing on loop reminding people of how to prevent the disease – may be a waste of time, effort and resources.

Experts say transmission of the virus via contaminated surfaces is exceptionally low – and that sanitizing outdoor areas such as parks and city streets is largely pointless and worse still, could even pose a danger to public health.

“The robots and street-spraying are performative acts designed to bolster public trust in government actions,” said Nicholas Thomas, an associate professor at City University of Hong Kong, who pointed to how Chinese authorities have long cited environmental contamination as part of their rhetoric that the virus may not have originated in China.

“It is a problem when politics dominates and diverges from the science of the pandemic response – more and more effort has to be placed on bolstering the politics through acts that do not necessarily increase the bio-safety of the affected populations to the same degree as the effort it requires to undertake them,” he said.

Imported virus?

Mass disinfection is part of a long-standing campaign in China to combat a Covid-19 transmission risk that much of the world has considered too minimal to warrant measures past hand-washing and maintaining disinfection of certain surfaces, like those in busy public places and where food is handled or Covid-19 patients are treated.

In a science brief last year, the US Centers for Disease Control and Prevention said scientific studies suggest that each contact with a surface contaminated with Covid-19 has less than a 1 in 10,000 chance of causing an infection. Such research has prompted many to view an overt focus on disinfection as “hygiene theater” as opposed to any meaningful disease prevention measure.

Mass disinfection has not been part of disease control measures in Western countries “because public health authorities followed the science,” according to Emanuel Goldman, a professor of microbiology at the Rutgers-New Jersey Medical School.

“(It’s) highly unlikely that any cases result from touching contaminated surfaces. The virus dies quickly outside an infected person … and transfers very inefficiently by fingers,” he said. “Hand washing with soap, or alcohol hand wipes, is all you need to get the incidence down to zero.”

In China, where stringent practices have focused on eliminating any spread of the virus, concerns about contaminated surfaces date back to the early months of the pandemic, especially after Chinese officials said an outbreak at a market in Beijing likely began due to a worker being infected from handling imported, frozen salmon contaminated with virus.

Though the World Health Organization says it’s “highly unlikely” that people can contract Covid-19 via food or food packaging, Chinese authorities have on numerous occasions pointed to cold-chain imports or other contaminated surfaces, like on airplanes or even international mail, as vectors of diseases.

This has lead to a raft of measures largely unique to China like testing the surfaces of imports for traces of virus and mass disinfection of frozen goods from overseas, while some cities have rolled out various orders to disinfect international mail and parcels – even though national health experts said earlier this year there was not sufficient evidence that such non-cold-chain items could carry the virus.

And as Beijing has sought to reframe the narrative around the origin of the coronavirus, first detected in China, officials have pitched a theory that the virus could have been imported on frozen goods in the first place – a hypothesis broadly dismissed by international experts.

While there is some evidence that the virus can remain infectious on frozen packaging, how countries may want to deal with this risk varies, according to Leo Poon, a professor at the University of Hong Kong’s School of Public Health.

“For countries which use elimination strategy, this is a significant risk. However, for most the countries now, this might not be significant at all,” he said.

But when it comes to touching regular surfaces, this is “not a major transmission mode for Covid-19,” he said, adding some disinfection in indoor settings could be a good idea.

Potential risk

In places like Shanghai, where resources are already stretched thin as the city struggles through a weeks-long lockdown, deploying volunteers and workers for disinfection purposes may put the focus on the wrong risk.

“There really is no role for mass disinfection of outdoor areas, pavements and walls. They are unlikely to be contaminated or cause transmission via a mucosal surface (like eyes, nose or mouth),” said Dale Fisher, a professor at the National University of Singapore’s Yong Loo Lin School of Medicine.

There can also be downsides to such work, according to Rutgers-New Jersey Medical School’s Goldman, who says that people can be harmed by exposure to harsh disinfection.

While the WHO supports disinfection such as wiping down areas like door handles in busy public places, WHO guidelines say “spraying disinfectants, even outdoors, can be noxious for people’s health and cause eye, respiratory or skin irritation or damage.”

Earlier in the pandemic, a group of Chinese scientists warned in a letter to the journal Science that the over-use of chlorine disinfectants runs the risk of polluting water and even putting ecosystems in nearby lakes and rivers at risk.

There are signs of similar concerns from Shanghai authorities, even as they press on with disinfection measures.

Late last month, officials put out recommendations for residents on how to disinfect, urging them against “spraying disinfectants directly on people,” using “canon trucks” and drones, or disinfecting outdoor air.

“These practices are essentially ineffective, and can cause health hazards and environmental pollution,” a Shanghai official said.