Asymptomatic people may be fueling the Coronavirus spread
For every person who tests positive, there’s likely another handful of asymptomatic people who don’t know they’re infected.
For every person who tested positive for the coronavirus in China, there were likely another five to eight asymptomatic people who didn’t know they had the infection, according to a new study. What’s more, these undocumented cases likely infected the majority of known — and thus likely more severe — cases.
As the world continues to battle the coronavirus known as SARS-CoV-2, the case counts continue to tick upward, rapidly filling online virus-spread maps with an unsettling coat of red. But underlying this very visible threat is an entirely different map outlining the movement of the coronavirus’s invisible vehicles: people who have very mild or no coronavirus symptoms at all.
To figure out just how many COVID-19 cases went undocumented, a group of researchers from five institutions across the world crunched the early numbers from China, where the outbreak first began.
The researchers created a mathematical model that analyzed the number of infections in 375 Chinese cities. Their model included travel time and distance traveled for people who participated in the country’s Chunyan, or Spring Festival Period — which began Jan. 10 — by analyzing data from 2018. They then simulated observations between Jan. 10 and Jan. 23 from this year before China implemented travel restrictions.
Based on the model, during this time period, China should have had 86% more cases of COVID-19 than what the country had reported. And those undocumented cases were about half as likely as the documented cases to infect another person.
Part of the reason is that people with mild cases or asymptomatic cases likely have lower amounts of virus in their systems that they could shed, co-author Sen Pei, an associate research scientist at Columbia University’s Mailman School of Public Health. However another study, though small in size, found that the coronavirus might be most infectious when symptoms are mildest, according to a Live Science report. The other reason is that these people sneeze and cough less than people with more severe diseases, Pei added.