The myth of widespread asymptomatic transmission


A new study published in the Journal of the American Medical Association (JAMA) by researchers from the University of Florida and University of Washington found that so-called “asymptomatic” or “presymptomatic” spread of COVID-19 is quite rare.

Controlling for differences, the meta-analysis of 54 studies covering over 77,000 participants found that SARS-CoV-2—the virus that causes COVID-19—has a “secondary attack rate” of 16.6%, higher than two notable coronavirus epidemics in recent years, SARS in 2003 (7.5%) and MERS from 2012 (4.7%). The secondary attack rate is the number of new cases divided by the number of total contacts from those cases, used to determine how likely it is an individual will contract the virus.

The authors noted that certain individuals were at higher risk of contracting the virus, such as those who lived in households with only one other person versus those who live with three others, adults more than children and spouses more than other relationships. 

They also describe symptomatic individuals as much more likely to transmit infection than those not experiencing symptoms. Researchers pinned the secondary attack rate of symptomatic cases at around 18%, but that of asymptomatic and presymptomatic cases at 0.7%. Though a notable difference, only four of the 54 studies included in the meta-analysis examined asymptomatic spread.

Nonetheless, it appears you are much more likely to spread pathogens when you are feeling sick and showing symptoms. This is an intuitive conclusion, but people got swept up in the fear of not knowing exactly how this virus behaves in the early days of the pandemic.

Of course, researchers had already begun tackling that question. A WHO review of four related studies from Brunei, China, Taiwan and South Korea published in early July found that “between 0% and 2.2% of people with asymptomatic infection infected anyone else, compared to 0.8%-15.4% of people with symptoms.” 

The authors point to “crowded indoor environments” like households as the highest-risk venues for transmission. This is not the first study to conclude this. In June, researchers had studied household spread and had identified it as a main driver of transmission. Even New York Governor Andrew Cuomo noted in an early May press conference that 66% of new hospital admissions in his state came from those who had remained at home.

Will Governor Mills and her cabinet take these (old or new) findings to heart? It appears unlikely; their goals have shifted yet their edicts have solidified. With households being a high-risk environment for transmission,  why institute (and continue indefinitely) a 9:00 p.m. business curfew, stealing wage-earning hours from struggling service workers while their would-be patrons scurry back to their homes?

Why order people to “stay healthy at home” when literally staying in one’s house can carry a higher risk of infection? 

There has always been a clear difference of risk between those with symptoms and those without, just as there has been a clear difference of risk based on age group or preexisting health factors. But the authorities couldn’t let the people know about this side of the science, as it would discredit their narrative. They worried that people wouldn’t take this virus seriously if the facts were known, so they stole personal agency and made the pandemic about compliance.

Could the new year usher a return to common sense and evidence-based governing? Based on Mills’ track record, it seems much more likely that she will double-down. Now that we are seeing the spike in “cases” Dr. Shah has warned about for the entire 10 months of the Civil State of Emergency, a result of their own strategy, they cannot yet admit their folly.

But, the inquisitive ones among us will continue to ask why the schools are still in flux, why the CDC won’t present the data on our highly sensitive COVID-19 PCR tests and why incidence of the flu has been near-zero this season. 

There are real questions to be asked of why our leaders led us down this path. Sadly, much of the Maine media has been a mere bullhorn for the party line, propping up the Mills administration’s persistent culture of fear.


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