2/ "There is great disparity in the way we think about and address different sources of environmental infection. Governments have for decades promulgated a large amount of legislation and invested heavily in food safety, sanitation, and drinking water for public health purposes"
3/ "By contrast, airborne pathogens and respiratory infections, whether seasonal influenza or COVID-19, are addressed fairly weakly, if at all, in terms of regulations, standards, and building design and operation, pertaining to the air we breathe."
Now that @WHO and @CDCgov have finally accepted *after a year of denial and delays* that airborne transmission is a major mode for COVID-19, it is time to review the history to try to understand why this response was so poor.
2/ Remember, the evidence is overwhelming that airborne transmission (1 to 1 in close proximity, and 1 to many in shared room air = superspreading) is the dominant mode of transmission.
3/ And probably we are being charitable by saying only "dominant." Can't find any real evidence that airborne is not 99%. Airborne can explain all the epidemiological patterns, while large droplets and fomites can't, and they are pathetically lacking ev.
1/ A radical shift today by @CDCgov, finally aligning itself with science on the modes of transmission, and throwing away the 1910 error of considering "close contact" a mode of transmission!
"Modes of SARS-CoV-2 transmission are now categorized as inhalation of virus, deposition of virus on exposed mucous membranes, and touching mucous membranes with soiled hands contaminated with virus," the new guidance reads."
3/ This finally follows science, most elegantly summarized by Prof. Yuguo Li of the Univ. of Hong Kong on this recent paper:
El video de la charla de hoy (30 min + 1 hr de preguntas) sobre "Métodos prácticos para estimar y monitorear el riesgo de contagio de COVID-19 cuando se comparte aire en interiores" se puede ver en YouTube:
2/ Y todo el artículo es muy interesante: las escuelas aumentan los contagios de los padres y maestros, pero se pueden reducir mucho con medidas correctas de protección:
3/ Lo cual es consistente con otras líneas de evidencia.
Como explicamos en este preprint, una escuela con la ventilación mínima de ASHRAE (o menos, que es lo típico) tiene bastante riesgo. Pero con mascarillas, ventilación, menos densidad, se mejora muchísimo. (Linea verde)
1/ UPDATES TO COVID-19 AEROSOL TRANSMISSION ESTIMATOR
We have just implemented several updates:
- added increased risk of variants
- made clearer how to enter vaccinated people
- added calculation of infection risk parameters
2/ The risk parameters allow quantitative decisions on which mitigations are needed to avoid outbreaks. See the thread from yesterday on that topic and paper:
3/ We also added a sheet with a quantitative version of the BMJ table (bmj.com/content/370/bm…). See sheet "Risk Table", where you can modify it for your conditions.