Commentary: The biggest threat from COVID-19 was in our own homes

PROVIDENCE, Rhode Island: A new trove of data from 7 million contacts have revealed that COVID-19 doesn’t spread the way many people think it does.

Researchers found that transmission was rare in encounters less than 30 minutes long, even if people got within six feet of each other. Many public spaces were never the threat they were deemed to be, and private homes were a major driver of disease spread.

That’s an important finding to amplify now, with a new variant - JN.1 - helping to lead a rising surge in cases just in time for the holidays. Even if you wouldn’t cancel plans over COVID-19, some people might make a different choice about a virus that’s still killing more people than the typical cold or flu.

“We all need accurate information so that we can do our own personal risk management,” said Christophe Fraser, an Oxford University professor and one of the study’s authors. “We can only really make good choices if we have accurate information to base those choices.”

THE 2-METRE RULE

The new data come from the UK where more than a third of the population used contact tracing apps. Though science wasn’t the intended purpose of these apps, created by Apple and Google, they turned out to be a great tool for studying transmission patterns. The results were published last week in the journal in Nature.

The findings go against many people’s germ-phobic instincts and sense of stranger-danger. “I think people overestimate the risk from supermarkets and very quick exposures,” says Fraser, “and they underestimate the risk from lengthy exposures ... friends, family, people at home, maybe going out to a restaurant.”

There are also important implications here for public health officials. The new data help explain why cases rose so steeply in the US even after the lockdown phase in the spring of 2020. Many people were suddenly in closer contact with friends and relatives in their own homes. Some increased the size of their households, adding significant others or extended family.

“Once you close everybody at home, you expect an initial spike of cases,” he said, because infectious people are with others 24 hours a day. With public spaces closed, some people also socialised in private spaces and kept the disease circulating.

Sometimes public health experts did the best they could with the information available, but other times they ignored good data. Fraser and his Oxford co-author Luca Ferretti both told me they’d argued from the beginning that the best way to use contact tracing apps would be to keep collecting data on who actually got infected and use it to improve guidelines.

The initial guidelines would trigger the app if you were within 2m of an infected person for more than 15 minutes. Then you’d be asked to self-isolate for 10-days, or to seek a test, depending on the policy at the time. The 2m rule was taken from decades-old data collected for tuberculosis. Whether it applied to this new virus was not clear. By April of 2020, scientists using manual contact tracing data showed that outdoor exposures were rare, that people in indoor spaces could get infected at greater distances, but that exposure was rare outside of at least 30 minutes.

People were focusing on distance, but duration is what really matters, Ferretti said. Some experts were saying this from the beginning, "but they were sidelined in the discussion".

HOME ISN'T A SAFE HAVEN WHEN IT COMES TO COVID-19

Perhaps in part because of a lack of good information, people tended to overestimate how transmissible the virus was. In household situations, that might have caused people to take too few precautions, thinking infection was inevitable. Household risk peaks at 30 hours of exposure, so even if you’d shared a bed with a spouse who developed a fever in the night, getting infected wasn’t inevitable if you isolated afterwards.

The reason the disease was hard to control wasn’t because it instantly spread to everyone who got within six feet of an infected person - it was hard to control because it could be transmitted by people before they had symptoms (or when they had no noticeable ones).

Ferretti said it’s not too late to benefit from the new data - even if it’s a bit dispiriting that home isn’t the safe haven many people initially thought.