Open your windows! Ventilation - the often overlooked measure with grave consequences
Scientists from the University of Colorado developed a Covid Airborne Transmission Estimator to look at different transmission scenarios. (El Pais, Oct 29, 2020) They analyzed the scenario of a choir rehearsal in Washington State, in the United States, in March. Efforts were made to maintain a safe distance and hygiene measures. But there were no masks, and no ventilation. They were singing and sharing space over a prolonged period. Just one infected person passed the virus on to 53 people in the space of two-and-a-half hours. Some of those infected were 14 meters away, so only aerosols would explain the transmission.
The scientists calculated that if masks had been worn, the risk would have been halved and only around 44% of those present would have been affected as opposed to 87%. If the rehearsal had been held over a shorter period of time in a space with more ventilation, only two singers would have become infected.
Similarly, a Chinese restaurant in Guangzhou, China, reported that people seated several meters away from an infected person caught the virus simply by being in the same enclosed space. (New York Times, April 20, 2020)
In June, various news outlets reported that there was no significant uptick in case numbers despite the worries of the Black Lives Matter demonstrators being so close together. Most of them were outdoors.
Some studies showing that just opening a window decreases the risk of infection. For example, in a bus outbreak, people sitting next to the window were not infected. (Science Focus, Dec 23, 2020)
Various scientists have called for stronger recommendations to ventilate, especially in the winter. Angela Merkel, the German Chancellor and a scientist by training, says the government’s AHA guidelines (distancing, hygiene and face coverings) will be extended to include ventilation.
Ventilation is one of the cheapest and most effective ways to help reduce the spread. Even if it's cold outside, opening the windows every now and then to let air circulate will greatly reduce the risk. So if people have to gather, set your timer, open the windows every 15 minutes or so, and pile on your scarves, sweaters and also -- as one scientist recommended -- thermal underwear!