London: Health officials at the World Health Organisation say there is not yet enough evidence to confirm a growing belief in Australia that the Delta COVID-19 can transmit in just five seconds rather than 15 minutes.
While the Delta variant — which first emerged in India and is currently dominant in Britain and now seeding an outbreak in Sydney — is known to be more transmissible than earlier variants, Australian officials have raised the possibility that the virus can spread in the amount of time it takes to breathe in.
Dr Mike Ryan, director of WHO’s Health Emergencies Program, said the concept was scientifically possible as the virus mutated to become “fitter” as it sought to replace previous versions.
It’s not know exactly how long it takes to infect someone with Delta virus by breathing on or near them.Credit:Istock
“It can shift the infectious dose, in other words the virus may be more efficient at infecting cells and you need less virus to cause an infection,” Dr Ryan told a virtual news conference from the WHO’s headquarters in Geneva on Saturday morning.
“How much virus do you need to be contaminated by or inhale before you reach a dose that causes you to have an infection? That’s not even known for the previous strains and it’s not fully understood for these newer strains - Delta strain included,” he said.
The Centres for Disease Control in the US says COVID-19 is predominantly spread when someone inhales an infected person’s fine respiratory droplets - which can remain suspended in the air for hours.
A person can can also become infected when they touch their mouth, nose or eyes if the virus has settled on their hands from exhaled respiratory fluids or contaminated surfaces.
Epidemiologist Maria Van Kerkhove said there were several groups studying the virus’ evolution in detail.
She said research had already shown that in all the mutations of COVID-19 the virus adheres to a person’s cell more easily.
“So that’s one of the reasons why we’re seeing increased transmissibility,” she said.
Researchers are also exploring whether the virus has adapted specifically to spread differently in healthcare settings.
NSW Chief Health Officer Kerry Chant has said a person infected with the Delta variant at Sydney’s Bondi Junction Westfield caught the disease in a “scarily fleeting” encounter, according to CCTV footage.
“They are clearly facing each other but it is literally someone moving across from each other for a moment, close, but momentary,” Dr Chant said.
According to Chant, two other people may have been infected in the same manner.
Similarly, Jeroen Weimar, Victoria’s COVID-19 commander, has also previously said infections were occurring in situations where people had very little contact and had simply brushed past each other in a small shop.
Sydneysiders were first advised but then required to wear masks following the detection of the “fleeting contact” cases.
The WHO said people needed to take a more “fastidious” approach to physically distancing, washing their hands and wearing masks because these basic behaviours guard against all strains of the virus.
Latika Bourke is a journalist for The Sydney Morning Herald and The Age, based in London.
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2021-06-26 00:32:23Z
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