Thread by @LongDesertTrain

1/19 Hand hygiene & surface cleaning as tools to prevent respiratory infections should go down in history as the "miasma theory" of the 21st century. Both captured something true but caused great harm when applied to the wrong category of disease.

https://twitter.com/hughes_eilir/status/1438545309026631681

2/19 The miasma theory accurately identified air as the source of much disease transmission but opposed germ theory and famously led experts to overlook contaminated water as the source of important GI diseases like cholera.

3/19 Similarly, hand hygiene (and maybe surface disinfection) help to control spread of GI pathogens but appear to do almost nothing to prevent transmission of respiratory infections. The disproportionate emphasis on them has likely done harm by... nature.com/articles/d4158…

4/19 ...stealing resources from interventions like improved ventilation, upgraded filtration, & portable air cleaners, all of which are actually effective in preventing the spread of airborne diseases like Covid. #COVIDisAirborne

https://twitter.com/jljcolorado/status/1435454183746859013

5/19 The CDC report below is often used—very misleadingly—by anti-maskers to argue against mask mandates. As I was reading it in order to debunk their claims, I was intrigued by some of the paper’s non-mask conclusions. wwwnc.cdc.gov/eid/article/26…

6/19 For example, when they looked at RCTs of hand hygiene in residential settings, they actually found a 5% higher risk ratio in the intervention groups than the control groups, though that result was not statistically significant.

7/19 One RCT found biweekly disinfection of toys & linen at a daycare center "was not significant in reducing detection of influenza virus, and it had no major protective effect on acute respiratory illness."

8/19 And an RCT in schools that implemented hand sanitizer use & surface disinfection showed "no major reduction in absenteeism related to respiratory illness," though the incidence of gastrointestinal illness declined.

9/19 The only study cited that claimed to show a real effect of hand hygiene on respiratory illness involved introducing running water and soap to a school in Egypt for the first time, so it really just shows the effect of introducing indoor plumbing.

10/19 Their conclusion: "We found no evidence that surface and object cleaning could reduce influenza transmission." But one study they included hinted that use of harsh cleaners could make matters worse.

11/19 A cross-sectional study found that use of bleach-containing cleaner at home & school was associated with a higher risk of several illnesses in children, including influenza.

12/19 Could obsessive cleaning with chemicals like quaternary ammonium compounds (QACs) & bleach actually facilitate the transmission of respiratory diseases? Given the research on air pollution & Covid, this seems like a real possibility.

13/19 A connection between air pollution and Covid-19 severity was noted as early as April 2020, when @HarvardChanSPH researchers found that even tiny increases in PM 2.5 are linked to remarkable increases in Covid death rates. theguardian.com/environment/20…

14/19 A similar connection between case fatality rates and air pollution was noted in China during the 2003 SARS epidemic. ehjournal.biomedcentral.com/articles/10.11…

15/19 I find it striking that the first three major Covid outbreaks in the world all occurred in regions surrounded by pollutant-trapping mountains, as noted by the author (@YaronOgen) of another April 2020 study on air pollution and Covid. theguardian.com/environment/20…

16/19 Since then, countless other studies have documented the link between Covid severity and air pollution, and it seems to be widely accepted that outdoor air pollution actually causes more Covid illness & death. lung.org/blog/covid-19-…

17/19 For example, a more recent Harvard study found that “thousands of COVID-19 cases & deaths in California, Oregon, & Washington between Mar & Dec 2020 may be attributable to increases in fine particulate air pollution (PM2.5)."
news.harvard.edu/gazette/story/…

18/19 Would it be any surprise to find that our enormously increased use of QACs, bleach, & other harsh surface cleaners (see study by @AminaSalamova_ & @GuomaoZheng below) during the pandemic has facilitated transmission & worsened Covid severity? pubs.acs.org/doi/10.1021/ac…

19/19 I don't think it's a stretch to posit that cleaning chemicals that, like air pollution, irritate respiratory passages, might also increase Covid transmission and severity, as air pollution does. I’m not aware of any studies on the matter, however. Seems worth looking into.