The CDC presents their evidence for Us to wear masks. https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/cloth-face-cover-guidance.html#recent-studies
The Scientists studied people from China. Some traveled from other places. People who came into contact with them did or did not get infected. The people who got infected had mild symptoms PMID: 32003551external icon different types of symptoms PMID: 32087116external icon or no symptoms but all tested positive. These findings are in concordance with reports that transmission may occur early in the course of infection PMID: 32074444external icon They assume Presymptomatic (eventually will develop symptoms ) transmission based on reports of individual cases in China. PMID: 32271722external icon
The asymptomatic individual is infected with SARS-CoV-2 but will never develop symptoms of COVID-19. PMID: 32491919external icon If a presumed transmission by an asymptomatic carrier are replicated, the prevention of COVID-19 infection would prove challenging. PMID: 32083643external icon
The simple solution to this conundrum is longitudinal testing . What differences might account for why 2 persons same age, sex, and health status have idiosyncratic responses to SARS-CoV-2 infection? Why isone asymptomatic, while the other lies near death in intensive care? At the moment, we simply do not know. PMID: 32491919external icon
New innovations in disease detection and prevention (beyond exhaustive contact tracing, mass testing, and isolation of asymptomatic contacts) may be needed.. Link
findings indicate that a large proportion of COVID-19 infections were undocumented prior to the travel restrictions. PMID: 32179701external icon And they fought travel restrictions.
Patients from Canada flew to Wuhan in January .Both tested positive for Covid-19. There were 350 passengers on board the airplane none of which tested positive for Covid-19 . PMID: 32392504external icon
Older adults are susceptible to severe COVID-19 outcomes. (As noted by all the problems in the nursing homes.) asymptomatic and presymptomatic infections might contribute to transmission in these settings. PMID: 32240128
This study provided visual evidence of spit when you talk into a box and to describe the effect of a damp cloth cover over the mouth to curb the emission of droplets. PMID: 32294341external icon
Concerning the possibility that the SARS-CoV-2 virus could be spread by conversation, in addition to sneeze/cough-induced droplets. They studied isolation rooms of patients who had covid . Personal collectors worn by samplers also were positive even though patients were not coughing while samplers were present.. https://doi.org/10.17226/25769external icon.
A homemade mask should only be considered as a last resort to prevent droplet transmission from infected individuals, but it would be better than no protection. PMID: 24229526external icon What type of materials are best for homemade masks PMID: 32329337external icon
Other types of homemade masks, especially those made of cloth alone, may be unable to block the virus and offer no protection against the virus . PMID: 32232986external icon
Our results indicate that surgical face masks could prevent transmission of human coronaviruses and influenza viruses from symptomatic individuals. This has important implications for control of COVID-19, suggesting that surgical face masks could be used by ill people to reduce transmission. PMID: 32371934external icon