With the Sydney cluster quickly spreading, it’s best we bust some generally held myths surrounding COVID-19.
Today, the Sydney cluster took another step in the wrong direction. The state recorded 145 new locally acquired virus Covid cases, with more than 50 believed to be infectious in the community. Yet, with Gladys Berejiklian and NSW Health warning that the figures will get worse, we should pause and bust two central myths that we’ve accepted as truth: Those with symptoms spread COVID, and the spread of the virus is 1.5 metres. As it turns out, neither of them are actually true.
New research, published in the Journal of the American Medical Association, has put a figure on the percentage of people who have spread COVID without actually realising that they have it. Horrifically, the data estimates that more than half of the transmissions have been from asymptomatic sources.
Back in November the Centres for Disease Control and Prevention (CDC), noted that the asymptomatic “estimated to account for more than 50% of transmissions.”
The lead author of the new study, Jay Butler, said the findings reinforce the importance of following public-health guidelines about mask-wearing and distancing.
“There was still some controversy over the value to community mitigation – face masks, social distancing, and hand hygiene – to limit the spread,” Butler told Business Insider. “This study demonstrates that while symptom screening may have some value, mitigation, as well as strategically planned testing of persons in some setting, will be a significant benefit.”
As Business Insider explained, “the researchers modelled potential COVID-19 transmitters in three groups: pre-symptomatic (people who hadn’t had symptoms yet), never symptomatic, and symptomatic. The researchers then modelled how much each group would transmit COVID-19 depending on the day people were most infectious. At baseline, they assumed people in all groups would be most infectious five days after getting exposed to the coronavirus. That’s what researchers have found to be the median incubation period – the length of time it takes for most people to develop symptoms after exposure.
“The model initially assumed that 30% of people were asymptomatic and that those individuals were 75% as infectious as people who were showing or would eventually show symptoms. Based on those assumptions, the results suggested that asymptomatic people alone were responsible for 24% of infections. But the researchers also modelled scenarios in which peak infectiousness occurred after three, four, six, and seven days, and they raised and lowered the percentage of asymptomatic people in the model, as well as their rate of infectiousness relative to other groups.”
As the study discovered, across most of the scenarios, those without symptoms (asymptomatic and presymptomatic) were found to transmit at least 50% of new infections.
“The proportion of transmissions remained generally above 50% across a broad range of base values,” Butler said, adding that the consistency of that finding was surprising, before suggesting that their model likely underestimates the real percentage of cases spread by the asymptomatic.
As Business Insider pointed out, “even in the most conservative estimate, in which peak infectiousness came seven days after exposure and asymptomatic people accounted for zero percent of transmission, the pre-symptomatic group still caused more than 25% of cases overall, according to the model.”
In addition to this, a study from Jeonju in southwestern South Korea has discovered that COVID can spread up to almost three times the range we’ve all accepted as canon.
Dr Lee Ju-hyung, who has authored the study, has re-created the conditions in a local restaurant in June, replicating the instance where a student became infected after five minutes of exposure from a distance of twenty feet, or 6 metres away.
As The Los Angeles Times noted, “the results of the study, for which Lee and other epidemiologists enlisted the help of an engineer who specializes (sic) in aerodynamics, were published last week in the Journal of Korean Medical Science. The conclusions raised concerns that the widely accepted standard of six feet of social distance may not be far enough to keep people safe.”
The findings illustrated how South Korea’s thorough (read: invasive) contact tracing policy was key in assisting the researchers to track how COVID moves through populations.
“In this outbreak, the distances between infector and infected persons were … farther than the generally accepted 2 meter droplet transmission range,” the study’s authors wrote. “The guidelines on quarantine and epidemiological investigation must be updated to reflect these factors for control and prevention of COVID-19.”
KJ Seung, an infectious disease expert and chief of strategy and policy for the nonprofit Partners in Health’s Massachusetts COVID response, spoke to The Los Angeles Times and noted that the official definition of a “close contact” — 15 minutes, within six feet, not only isn’t foolproof, it may spell trouble as the Northern Hemisphere faces winter, and the extra transmission colder weather brings.
“There’s a real misconception about this in the public,” said Seung, who was not involved in the South Korea study. “They’re thinking, if I’m not a close contact, I will magically be protected.”
Seung also said the study was the evidence that contact tracers the world over need to widen their search when looking for individuals who have been potentially infected and to better alert those who have been exposed, but have been classified as “lower risk”, who figured that they were safe.