And given we’re probably going to be living with COVID-19 for a long time, we need to get better at it.
“I still feel there are a lot of people who think of risk in terms of this binary framework: something is either risky or completely safe,” Dr Vally says.
“If you think in those terms, the risk is you worry a lot about things that are very low risk. And if you worry disproportionately about the wrong things, you won’t worry about the right things.”
This does not mean you should stop washing your hands; people who wash their hands six to 10 times a day cut their risk of catching coronaviruses substantially.
What Dr Vally argues is that your focus should be on the risks that matter most – personal contact, over time, inside.
Your risk of catching the virus from surfaces is relatively low, as is your risk from walking past someone who is infected. But spend time inside with an infected person – at work, at home or at the pub – and your risk rockets.
In the pandemic’s early stages, very little was known about how SARS-CoV-2 spread. Scientists had to turn to what was known from flu and SARS.
That meant early public health messages gave similar focus to catching the virus from people and picking it up from surfaces, says Dr Vally.
Many people, such as Rod Lamberts, deputy director of the Australian National Centre for the Public Awareness of Science, found themselves taking the strange step of sanitising their groceries.
“I was really worried about surfaces,” says Dr Lamberts. “But the advice on that has now changed.”
In fact, the evidence now suggests that while hand hygiene is important, it is close contact with another sick person, rather than touching an infected surface, where most of the risk lies.
“Contact spread [via] lift buttons and surfaces, while real, is probably overblown,” says Associate Professor Craig Dalton, an epidemiologist at the University of Newcastle.
Evidence suggests we prefer easy or familiar measures – such as repeated hand washing – to more difficult practices such as avoiding friends, despite the much greater risk posed by personal contact.
“If something is easy and socially acceptable, you’re more likely to do it, [like] hand washing, wearing masks. The social stuff is really hard, and it gets harder to maintain as time goes by,” says Associate Professor Mel Taylor, an expert on how humans think about risk based at Macquarie University.
Dr Vally has a formula for working out risk: distance plus time.
The longer you spend close to someone, the higher your risk.
Contact inside, particularly in poorly-ventilated rooms, is about 20 times more risky than contact outside.
That’s why spending time in your home with someone who does not live there – or worse, hosting a party – remains among the highest-risk activities.
Going to a bar is also up there, as is attending a large religious service. Crowded public transport is also likely to be highly risky.
But if an infected person walks past you on the street, they will be gone so quickly your chances of falling sick are low.
A South Korean call centre outbreak bears this out: nearly all the 97 people who fell sick had desks near each other; there was almost no spread in elevators and the building’s lobby.
“If you walk past someone in the street, that is a low-risk activity. We shouldn’t obsess,” Dr Vally says.
Liam is The Age and Sydney Morning Herald’s science reporter