Covid loses 90% of ability to infect within 20 minutes in air – study

Coronavirus loses 90% of its ability to infect us within 20 minutes of becoming airborne – with most of the loss occurring within the first five minutes, the world’s first simulations of how the virus survives in exhaled air suggest.

The findings re-emphasize the importance of short-range Covid transmission, with physical distancing and mask-wearing likely to be the most effective means of preventing infection. Ventilation, though still worthwhile, is likely to have a lesser impact.

“People have been focused on poorly ventilated spaces and thinking about airborne transmission over meters or across a room. I’m not saying that doesn’t happen, but I think still the greatest risk of exposure is when you’re close to someone,” said Prof Jonathan Reid, director of the University of Bristol’s Aerosol Research Centre and the study’s lead author.

View the complete source version on theguardian.com: https://www.theguardian.com/world/2022/jan/11/covid-loses-90-of-ability-to-infect-within-five-minutes-in-air-study

Very impressive scientific findings coming out of Univ. of Bristol last month with significant implications for COVID airborne transmission.  This study by Oswin et al. at the Univ. of Bristol used a novel aerosol levitation method that allowed them to tightly control the period of time aqueous droplets containing SARS-CoV-2 virus remained suspended in air, and the loss of viral infectivity observed as a result of this “artificial aging” of the aerosols.  Their results found that the SARS-CoV-2 virus (regardless of the strain) lost most of its infectivity quite rapidly, 90% within the first 20 minutes in the air, with most of this loss occurring in the first 5 minutes.

One of the many implications of these findings is that meaningful approaches to preventing airborne transmission of COVID likely take one of two forms:  either a collective approach that involves very high rates of ventilation in the form of very high air changes per hour (ACHs) of the sort that’s generally not found in homes or commercial buildings; or an individualized approach such as masks that provide protection for the breathing or breathing zone of each individual.  Technologies that do not process the entire volume of air in a room on a time scale comparable to the apparent half-life of the SARS-CoV-2 virus (based on this study) are likely just moving around or filtering viral particles that no longer pose an infection risk anyway.