KUALA LUMPUR: The effectiveness of public sanitisation exercises is still a matter of debate. While some countries have adopted it as a method to control the spread of Covid-19, others have chosen to steer clear due to potential health risks.
Although Malaysia has adopted it since the onset of the Movement Control Order (MCO), experts are still weighing the facts, especially on outdoor sanitisation.
Infection control expert Dr Tengku Zetty Maztura Tengku Jamaluddin confirmed that the chemicals and their concentration administered by the authorities were recognised by the World Health Organisation (WHO) as being able to effectively kill the virus.
"The solution (concentration) is between low and intermediate strength, but even a mild solution can deactivate and kill SARS-CoV-2," she said, referring to the virus that causes Covid-19, which could live for hours on porous surfaces, such as cupboards, three or four days on plastic and stainless steel, and up to seven days on discarded face masks.
Dr Tengku Zetty, who is a medical lecturer in Universiti Putra Malaysia, however, said that WHO, in its interim report on the subject on May 15, did not recommend the sanitisation of outdoor surfaces.
"How effective it is, is dependent on how thoroughly a place is cleaned before the solution is applied. Disinfectants can only kill and deactivate microbes. Cleaning, on the other hand, removes dirt and debris (that can harbour or host them).
"Simply said, you can't mop a dirty floor with a cleaning agent and expect the germs to die."
She said in terms of cost-benefit analysis, such exercise was more effective indoors, even though the same WHO report also spelt out that it did not recommend such exercise indoors, as the chemicals used might be detrimental to human health.
"As the virus is more likely to thrive longer in closed and contained environments, there is more benefit for it to be done in such spaces, where you know all the surfaces and crevices."
Dr Tengku Zetty said if the authorities felt that they needed to sanitise an outdoor area, it should be done in a targeted and thorough manner by following the health authorities' standard operating procedures.
She said like other microorganisms, the Covid-19 virus could adapt to withstand disinfectants.
This, she said, was because the viruses, let alone a supervirus like SARS-CoV-2, had been observed to have the ability to mutate for survival and propagation.
In its report, WHO said spraying or fumigating outdoor spaces, such as streets or marketplaces, was not recommended to kill the Covid-19 virus or other pathogens because disinfectants are inactivated by dirt and debris.
The document stated that it was feasible to clean and remove all organic matter from such spaces.
It further said that spraying on porous surfaces, such as sidewalks and unpaved walkways, would be even more ineffective.
"Even in the absence of organic matter, chemical spraying is unlikely to adequately cover all surfaces for the duration of the required contact time needed to inactivate pathogens.
"Furthermore, streets and sidewalks are not considered reservoirs of infection for Covid-19. Besides, spraying disinfectants, even outdoors, may be harmful for human health," read the WHO report.
Epidemiologist Professor Dr Sanjay Rampal said the effectiveness of public sanitisation was questionable for a number of reasons.
"The effectiveness of indiscriminately spraying or disinfecting using chemicals to kill the virus in public areas has been questionable for some time now, even before it was used here."
He said the method might not actually be killing all harmful viruses or bacteria in the entire environment or living spaces.
This was because outdoor areas were extensive, comprising homes, neighbourhoods, shops, transportation, workplaces and others.
"There is an argument that public sanitising may reduce the amount of viruses in an area.
"However, if we 'carpet bomb' all organisms in an area, we may actually kill many good organisms along with the harmful ones."
The Universiti Malaya lecturer also said that if only one part of the environment was sanitised, there was a possibility that the virus be brought back to the sanitised area from unsanitised areas.
He also cited the Unites States Centers for Disease Control and Prevention, which said outdoor areas generally required regular cleaning, and did not require sanitisation.
It said that spraying disinfectant on sidewalks and in parks was not an efficient use of disinfectant supplies, and it had not been proven to reduce the risk of Covid-19 infection to the public.
"As such cleaning and maintaining a hygienic environment using existing practices is important. However, we don't recommend mass spraying of disinfectants on public areas," he said.