Public health measures in the United States to mitigate the spread of Covid-19 have thus far focused primarily on social distancing, hand and surface hygiene, and mask use.
Since coronavirus has been known to be an airborne virus since the MERS outbreak of 2015, the former of these measures are thought to be relatively ineffective in preventing the spread of Sars-Cov-2, the virus responsible for Covid-19.
Thanks to recent research conducted by the University of Waterloo, we can now conclude that even mask use (at least using the masks recommended by the US CDC*) is likely less effective than simply opening a window. According to the abstract of the study:
The results also suggest that [...] even relatively low air-change rates lead to lower aerosol build-up compared to the best performing mask in an unventilated space.
Ventilation is substantially more palatable for the general public than social distancing or even mask use and high levels of compliance can be expected, yet while Canada and much of Asia have made ventilation and air filtration a cornerstone of their Covid mitigation measures the US has not adopted ventilation enhancement to any significant degree. (The most shocking example of the lack of focus on ventilation I recently experienced was visiting a certain major research university, the buses were operating with windows completely closed.) The only real investment in ventilation or air purification has been for schools, provided in the American Rescue Plan; while this is certainly a good thing, it means nothing unless mitigation extends into the communities children live in.
Educating the public on effective ventilation measures for the home (where up to 70% of infections happen) or small businesses and providing funding to large public places for efficient ventilation and filtration systems such as air-to-air heat exchangers or HEPA filtration should be a high priority.
(Ventilation also has the added benefit that anti-vaxers can’t circumvent the measure by doing something stupid like wearing a mesh or lace mask and infect everybody around them!)
* Regarding mask use, the results of the study suggest that ordinary surgical masks and cloth masks provide very little mitigation (~10%) of aerosol generation while higher efficiency masks provide excellent mitigation (upwards of 60%). The US CDC’s refusal to adopt a standard for and recommend the use of non-occupational respirators similar to the South Korean KF94 or Chinese KN-95 and instead endorse the ASTM F3502-21 standard, a standard which requires absolutely no objective testing of external or internal leakage and has a filtration requirement so low it is entirely useless, will likely prove to have been another misstep in controlling the spread of covid in the United States.