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An Ordinance of the County of Allegheny, Commonwealth of Pennsylvania, establishing a uniform Countywide system of mask requirements and exemptions for public and private gatherings.
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WHEREAS, the Centers for Disease Control (CDC) clearly and eloquently summarized many of the benefits of masking in their publication The Science of Masking to Control COVID-19, CDC, 11/16/20 (attached); and
WHEREAS, among the findings made by the CDC are the following:
· Infection is spread primarily through exposure to respiratory droplets exhaled by infected people when they breathe, talk, cough, sneeze, or sing.
a. Most of these droplets are <10 µm, often referred to as aerosols.
b. The amount of these fine droplets and particles increases with volume of speech (e.g., loud talking, shouting) and respiratory exertion (e.g., exercise).
· 40-45% of infected people are estimated to never develop symptoms, and among people who do develop symptomatic illness:
a. Transmission risk peaks in the days just before symptom onset (presymptomatic infection) and for a few days thereafter.
b. Accordingly, the number of infections transmitted peaks when virus levels peak.
· Most SARS-CoV-2 infections are spread by people without symptoms.
a. CDC and others estimate that more than 50% of all infections are transmitted from people who are not exhibiting symptoms.
b. This means, at least half of new infections come from people likely unaware they are infectious to others.
· Cloth masks provide source control, by containing exhaled droplets.
a. Cloth masks block most large (>20-30 µm) exhaled respiratory droplets.
b. Multi-layer cloth masks substantially block respiratory droplets <1-10 µm - Comprise the greatest fraction of exhaled respiratory droplets.
c. Reductions in exhaled aerosols overall when cloth masks are used are as high as 50-70%.
d. Some cloth masks perform on par with surgical masks for exhaled aerosols.
· Cloth masks also filter inhaled droplets...
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