The Centers for Disease Control and Prevention has changed its policy and is now advising everyone, whether or not they have symptoms of COVID-19, to cover their face with a face mask or cloth covering whenever social distancing is difficult to maintain. To be clear, the CDC is not saying you should wear a mask wherever you go, but rather in places where people congregate, including grocery stores and public transportation and ride-shares. The shift in recommendations reflects growing evidence that COVID-19 can be transmitted by a person’s exhalations and normal speech but also the fact that people are not effectively covering their sneezes and coughs.
We can’t stay locked in our homes indefinitely. When the day comes to restart our normal lives, we should do everything possible to prevent the coronavirus from spreading uncontrolled through our communities. That is why we need to start a serious conversation about Covid-19 protection now.
The stealth virus
COVID-19 middle name should be stealth. People can be shedding virus for one to three days before showing any symptoms including no coughing, sneezing or fever in what’s called presymptomatic transmission. A Singapore study suggests that 10% of infections are attributable to presymptomatic spread. A study of the 3,711 passengers and crew on the Diamond Princess cruise ship indicates that close to 1 in 5 COVID-19 carriers never develop symptoms. Some these people transmit the virus through asymptomatic transmission. The proportion of infected people that never develop symptoms could be more like one-third for the general population that is younger and healthier than typical cruise takers.
The virus ability to spread so easily from one person to the next is why people are being asked to physically distance themselves from one another. But people still have to go out to get essentials at places where people gather. If a person is not coughing or sneezing, how are they spreading the virus? One way is by contact. The virus lives on the mucous membranes in the throat and nose. With people touching their faces every two-and-a-half minutes, on average it’s easy to see how the virus gets on our hands, and then we can spread it to commonly used surfaces like door knobs, a plastic handle in the subway or someone else hand. Steel and plastic surfaces can harbor live virus for three days.
Although Covid-19 is a novel disease, it is caused by the SARS-CoV-2 virus, which is closely related to the virus that caused the SARS epidemic 17 years ago. However, since Covid-19 true genetic identity was not widely publicized until recently, influenza research probably shaped doctors’ initial opinions about face masks instead. What does the actual science say about SARS?