The novel coronavirus SARS-CoV-2, better known as COVID-19, has now forced most of us into our homes for weeks. Many epidemiologists and public health experts have commented about the importance of staying at home and social distancing, but why exactly does it matter? Surely if I’m healthy, I should be able to go out with my friends, right? A recent paper published in Science highlighted the importance of staying at home in these crucial times, even if you’re feeling well. They found that people with mild, limited or even no symptoms at all were estimated to have caused the majority of severe COVID-19 infections and the wide geographic spread of COVID-19.
In the study, scientists constructed a mathematical model to match the observations of reported infection in China. They separated infections into two categories in their model: documented and undocumented. Documented infections are reported infections, often with severe symptoms, while undocumented infections are unreported infections due to having mild, limited or no symptoms. After obtaining the best-fit model that closely simulated the daily increase in infections in China, they found that undocumented infections were only half as contagious as severe infections. However, 86% of all infections were undocumented and, most importantly, a whopping 79% of severe infections were caused by these undocumented infections. These numbers were estimated using the statistics provided by China, but they also correctly matched the reported infections among foreigners evacuated from Wuhan.
In order to further emphasize the gravity of undocumented infections on the overall transmission of COVID-19 infections, they created a new model, where undocumented infections are no longer contagious (i.e. a situation whereby people with little or no symptoms are distancing themselves from other people). They found that reported infections could have been reduced by 78.8% in China and 66.1% in the city of Wuhan. Additionally, the number of cities with the infections would also have been reduced, limiting the geographic spread of COVID-19.
Although these numbers are just estimates, they shine a light on the importance of social distancing, even for people who are healthy. Furthermore, the practice of social distancing has also been proven useful in real life, as the spread of COVID-19 slowed substantially in China after they imposed travel restrictions and social distancing. Therefore, if you’re wondering if you should be going out to the bar to hang out, the appropriate answer would be no!
Managing Correspondent: Wei Li
Press Article: To Beat COVID-19, Social Distancing is a Must. National Institute of Health.
Scientific Article: Substantial undocumented infection facilitates the rapid dissemination of novel coronavirus (SARS-CoV2). Science.