BEWARE OF SYMPTOMLESS SUPERSPREADERS

A just-published research article in the Proceedings of the National Academy of Sciences (PNAS) reveals some striking new information about how the coronavirus spreads. A study testing thousands of people at the University of Colorado, Boulder, found that the distribution of virus particles among symptomless individuals matched the distribution among people hospitalized for Covid-19, with a few individuals in both groups carrying enormous numbers of virus particles and so having the potential to act as COVID-19 superspreaders. In other words, some people with no COVID-19 symptoms at all can spread the disease as easily as the most contagious hospitalized patients.

Virus loads in asymptomatic people matched those in hospitalized patients

Credit: Yang et al., University of Colorado, Boulder

The researchers found that, regardless of symptoms, just two percent of people who test positive for the coronavirus carry 90 percent of the virus particles circulating in a given population. "The highest observed viral load was over 6 trillion virions [complete, infective virus particles] per Ml, which was only observed in one individual," they write. "It is remarkable to consider that this individual was on campus and reported no symptoms . . .." 

They add that just 10 percent of symptom-free people who test positive for the virus, plus 14 percent of hospitalized Covid-19 patients account for 99 percent of circulating, active virus particles. 

In addition to such potential super-carriers, the researchers estimate that 50 percent of symptomless individuals who test positive for the coronavirus carry enough virus particles in their saliva to spread COVID-19 to to others.

These finding have several important implications. One is that being symptom free does not guarantee that someone isn't a COVID spreader or super-spreader. As more people get vaccinated and people become more relaxed about mask-wearing social distancing and avoiding groups and crowds indoors, it's very likely that we'll see continuing outbursts of Covid cases seeded by such symptomless but highy contagious non-vaccinated individuals. 

Anyone concerned for their own safety or that of their family, friends or contacts should probably not be in a hurry to stop wearing a face mask to minimize their own risk and the risk they potentially pose to others.

A second, public-health implication is the importance of continued, widespread screening, including of people without any COVID symptoms. ". . . it is imperative that we find virus supercarriers, and inform them of their infection status in a way that is fast, easy, and accessible," the researchers write. "Finding viral supercarriers will have a disproportionately large impact on curbing new COVID-19 infections."

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REA/5-10-21