In a new study, researchers found the asymptomatic spread of the coronavirus is likely both common and significant.
The finding may help dispel lingering doubts about whether to be concerned that people without COVID-19 symptoms are spreading the disease.
The research was conducted by a team at the Georgia Institute of Technology.
How strongly does asymptomatic spread contribute to the COVID-19 pandemic’s curve?
The new study addressed the question with mathematical modeling and concluded that this depends on how asymptomatic spread affects what is called the generation interval for new infections.
Simply put, the generation interval is how long it takes for a person infected today to infect the next person.
Knowing where these intervals fall allows researchers to calculate a more accurate value for R0 (R naught), a number that indicates the pandemic’s inherent strength of contagion in the absence of measures like distancing or masks to push it down.
R0 is used to project how long the pandemic can last, how high the infection curve can go, and how many people in total could get sick and die.
But unlike highly visible data such as new cases per day, hospitalizations, or death toll, asymptomatic spread moves in the shadows because those cases very often remain unrecorded.
Documenting them would take a large-scale virus and antibody testing and meticulous contact tracing.
That makes it challenging to accurately measure the real-time impact of asymptomatic spread.
In light of this, the researchers calculated how a broad range of asymptomatic spread scenarios would affect the nature of the generation interval and the course of the pandemic.
They found that asymptomatic spread’s contributions can reduce or raise the R0 calculation dramatically.
That would mean that if current assumptions about asymptomatic spread are very inaccurate, R0’s value and the resulting projections of the pandemic’s length and severity would be, too.
Though the study was not about mitigations like distancing and masks, the team said both pushbacks on the virus’s innate strength of the transmission.
If a society can push the strength below 1—one infected person infecting just one other person on average—the pandemic starts to fade away, a success a few countries have already achieved.
One author of the study is Joshua Weitz, a Georgia Institute of Technology professor.
The study is published in Epidemics.
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