'Silent Spreaders' May Be Responsible For Half Of U.S. COVID-19 Cases

Presymptomatic and asymptomatic carriers might be contributing to half of all COVID-19 cases

A new study claims that half of all COVID-19 cases in the U.S. are being contracted from “silent spreaders” aka asymptomatic carriers or pre-symptomatic carriers, which means people with COVID-19 in the days before their symptoms begin to show. The study, published in the Proceedings of the National Academy of Sciences, has shown that the virus is most contagious in the pre-symptomatic phase and that effective contact tracing would be needed to truly flatten the curve.

The study used existing research on the coronavirus and how it’s contracted and found that pre-symptomatic people would account for 48% of transmission and asymptomatic people account for 3.4% of transmission. In layman’s terms, people are getting COVID-19 from coronavirus carriers interacting with others just days before their major COVID-19 symptoms kick in.

The bad news here is that even if all symptomatic patients are isolated “a vast outbreak may nonetheless unfold.” The study says that the only way to implement their findings and truly contain the virus is with contact tracing and isolating (which is where you call people that have been in contact with a COVID-19 positive person and tell them to get tested and self-isolate). However, contact tracing is being rolled out in fits and starts, and states like Massachusetts that announced ambitious statewide contact tracing programs are now scaling back, claiming the program was “unreliable.” According to the study, “over one-third of silent infections must be isolated to suppress a future outbreak below 1% of the population” and since most people aren’t just willy nilly getting tested on their own to see if they might have COVID-19, we have to rely on government-organized contact tracing programs.

The good news is that this study provides some clarity on asymptomatic and pre-symptomatic carriers as just last month the World Health Organization gave very conflicting information about asymptomatic carriers, first saying it was “very rare” for asymptomatic carriers to spread the virus, then backtracking and saying they don’t actually have enough information about asymptomatic carriers just yet to make that statement. This new study, at least, clarifies that it’s really the pre-symptomatic carriers that are doing most of the harm and brings up other questions about things like temperature checks and how they’re unlikely to be helpful in determining who has COVID-19.

So what can you do with this information? CNN points out that randomly getting tested may not be the answer, but you know what is? Masks and social distancing. Wear a mask whenever you leave your house and even if you’re wearing a mask, try to stay six feet from anybody who doesn’t live in your household.