SEOUL – Here, in one of only two countries that are successfully controlling a large outbreak of the novel coronavirus, scientists have discovered a key fact about the virus: IT COMES FROM MOUTHS!
Scientists deduced this by considering the largest clusters that have arisen in what has otherwise been a very successful campaign against the virus: churches and a call center. Both involved people opening their mouths to speak or sing in close proximity indoors, expelling large amounts of respiratory droplets from their mouths. Given that a person expels more respiratory droplets in two seconds of talking than in a cough (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2843952/), viral droplets quickly fill crowded, poorly ventilated spaces. Other clusters reported internationally, such as cruise ships, conferences, and parties, are similar situations where people talk and eat in close proximity indoors.
Particularly noteworthy is the case of the Skagit Valley Chorale in Washington State (https://news.yahoo.com/choir-decided-ahead-rehearsal-now-023414705.html). Within a 2.5 hour rehearsal, 45 members of a 60 member choir managed to get infected (with two dead so far), despite the use of hand sanitizer and avoidance of all physical contact. Given this and the church outbreaks, it seems that singing may pose a special risk, with a greater quantity of respiratory droplets propelled to greater distances than ordinary speech.
Since people need their mouths in order to breathe, eat, and drink, tackling the virus isn’t as simple as sewing our mouths shut—but public health officials here as well as across the region suggest that mouths be covered in public so that your respiratory droplets don’t reach other people near you. A simple mask, made of almost any material, acts as a prophylactic so that you don’t spread the virus to those around you, if you’re pre-symptomatic or asymptomatic.
Is it a 100% solution? No. Masks aren’t perfect, but neither are condoms. People can misuse them, they can leak. But, like condoms, they are a cheap and only slightly socially awkward tool to avoid spreading a dangerous infection.
So stay at home yes, but if you can’t or aren’t, and you’re around other people—COVER IT UP!
Great posts. I’m also in a country that requires mask wearing and we are wondering WTF is up with Western countries and the WHO telling people masks aren’t effective. I hope there will be some soul-searching when this is all over.
I’d also point out that in the Xie et al. 2009 article that you cite, having food colouring in your mouth increased droplet production while talking by 3x (from around 750 to around 2200). The particular food colouring used had a salty taste, so this was probably due to the increased saliva or mucus production from having a flavorful substance in the mouth. To the researchers, this was an annoying obstacle to their measurement methodology, but it indicates something very important which is that eating while talking may multiply by a factor of 3 the already high droplet production from talking.