Where you’re most likely to catch COVID

It’s not what publicans want to hear but spending prolonged periods with other people indoors remains the most likely way of COVID-19 spreading.

“It’s a combination of indoors, which is 20 times more dangerous … in terms of transmission risk than outdoors, and the length of time you spend,” says Victoria’s chief health officer Brett Sutton.

Professor Sharon Lewin, of the Doherty Institute, says this is why Melbourne’s strict lockdown is working and must continue.

“As we release the brakes on (lockdown measures), we’re also pressing the accelerator, because we’re allowing people to mingle.”

Speaking on ABC Local Radio on Monday, she said she was less concerned by the hordes of Melburnians who got out of the house at the weekend when the sun shone and the temperature rose into the 20s for the first time in months.

Being outdoors reduced the risk of transmission dramatically, she said. And warmer, sunnier weather also helped.

Prof. Lewin said a Royal Melbourne Hospital analysis of 200 staff revealed that a well-ventilated room also makes a difference to transmission rates. She said really simple interventions had affected the rate of cases among healthcare workers. Staff need to put on and take off personal protective gear (PPE) with absolute rigour and not mingle with colleagues after doing so. Even having a cup of coffee in the same room as others after removing PPE increases the chances of transmission.

Victoria recorded just 11 new coronavirus cases on Monday, which Premier Daniel Andrews said made it a “great day”. But that number is still too high to cut restrictions.

“If you open up today, you won’t see the effects of that for two or three weeks. If we do it [open] too fast, we run the risk of losing control …”

He said declining case numbers showed the strategy of stage four lockdown in Melbourne was working and adhering to it would avoid Victoria “bouncing in and out of lockdown throughout 2021”.

He admitted there was a conservatism to his strategy, but following scientific advice was necessary because the stakes were so high.

A recent cluster of 43 cases in Melbourne’s south-east occurred after families broke lockdown to gather at each other’s houses.

Prof. Lewin said experts were reliant on “really good testing and tracing”.

“But that’s in the middle of a lockdown … It’s harder with people moving around the community.”

She said if Australian states agreed on a definition of coronavirus hotspots, the tracing system could pounce on new infections.

Curtin University infectious diseases professor Archie Clements told The New Daily the greatest danger came from being in proximity to someone in an enclosed space where the circulation of air is limited and possible virus-containing droplets can remain in the air for longer than in an open area.

“The smaller the space, the higher the risk,” said Professor Brian Oliver, head of the Respiratory Molecular Pathogenesis Group at the University of Technology Sydney.

He said visiting a place such as a shopping centre or a café probably increased the risk of getting the virus.

“If you are going to go out, you can’t forget that outside is still a risky place,” Prof. Oliver said.

In August, Professor Devi Sridhar, chair of global public health at the University of Edinburgh, told The Guardian that poor airflow, difficulties in distancing from others, and prolonged exposure made indoor settings riskier.

“Pubs and bars are quite high risk; it goes back to the conditions inside – poor ventilation and a crowded setting,” said Prof. Sridhar.

“It’s probably going to depend a bit on your ventilation and airflow, but I think a crowded restaurant is not a good idea. Anything that is outdoors, even outdoor hospitality, I am quite relaxed about, especially if there is a breeze.”

The Guardian quoted a Japanese research paper: “Many COVID-19 clusters were associated with heavy breathing in close proximity, such as singing at karaoke parties, cheering at clubs, having conversations in bars, and exercising in gymnasiums.”

A British study reported that most clusters of COVID-19 infections were linked to indoor settings. It identified risks associated with meat-packing factories where the cold, prolonged close proximity of workers and the need to shout over the noise of the machines may increase the risk of transmission.

Prof. Lewin said the best case scenario for the widespread rollout of a COVID-19 vaccine was mid-2021 and just 30 to 50 per cent efficacy might be acceptable for the first vaccines.

The advice from the US Centers for Disease Control and Prevention is simple: “In general, the more closely you interact with others and the longer that interaction, the higher the risk of COVID-19 spread.”

CDC guidelines for going outdoors:

  • Interacting with more people raises your risk.
  • Being in a group with people who aren’t social distancing or wearing masks increases your risk.
  • Engaging with new people (e.g. those who don’t live with you) also raises your risk.
  • Some people have the virus and don’t have any symptoms, and it is not yet known how often people without symptoms can transmit the virus to others.
  • The closer you are to other people who may be infected, the greater your risk of getting sick.
  • Keeping distance from other people is especially important for people who are at higher risk for severe illness, such as older adults and those with underlying medical conditions.
  • Indoor spaces are more risky than outdoor spaces where it might be harder to keep people apart and there’s less ventilation.
  • Spending more time with people who may be infected increases your risk of becoming infected.
  • Spending more time with people increases their risk of becoming infected if there is any chance that you may already be infected.

Activities are safer if:

  • You can maintain at least 6ft (1.82m) of space between you and others. COVID-19 spreads easier between people who are within 6ft of each other.
  • They are held in outdoor spaces. Indoor spaces with less ventilation where it might be harder to keep people apart are riskier.
  • People are wearing masks. Interacting without wearing masks also increases your risk.

When do you think we will safely enjoy restaurants and pubs and crowded spaces again? Are you happy to go to a shopping mall again?

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Written by Will Brodie

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