One of the largest research on the subject, conducted on over 300 thousand people in Bangladesh, has analyzed masks: promoted the effectiveness of surgical ones, rejected those of cloth
An extensive investigation confirms this: le masks surgical they are effective in countering the contagion from Covid-19. The research, conducted in Bangladesh on hundreds of thousands of people, he analyzed the role of these devices, combined with distancing and other rules. Researchers from Yale University, along with other US universities, have estimated the impact as a personal protective measure, in addition to the others. They also compared the masks surgical with the homemade ones, of fabric. Result? The use of the former has been associated with a reduction in the prevalence of infections, while the handmade ones had almost no impact. The study is published in the journal Innovations for Poverty Action Working Paper.
An articulated study
Researchers got involved more than 340 thousand Bengalis with the aim of promoting the use of masks and making them more accessible. One of the purposes of the research was in fact to understand if informative interventions targets may increase adherence to this protective measure for coronavirus containment. The volunteers were divided into two large groups, of which only the first received for free masks – surgical or cloth, all of 3 layers – and repeated information, during the trial, on the importance of their use and on how to wear them correctly.
In the trial, the authors assessed compliance with the proposed measures. The novelty concerns the fact that this assessment it happened in a manner direct – and not as often happens, through information reported by the participants – with regular meetings of health workers at the most popular meeting points in the villages (supermarkets and mosques). Meanwhile, the researchers monitored the health of citizens, detecting any symptoms and carrying out subsequently test due to the presence of antibodies anti Sars-Cov-2. Once these tests were collected, the experts put together the data on the use of masks with those on the prevalence (spread) of Covid-19.
The researchers wanted to understand if and to what extent an information campaign on the use of masks was successful. The results are very positive: in the villages where they intervened usage has tripled, with 42% of the people who wore them against only 13% in the control villages.
Within the areas that received the intervention of the specialists, with the free masks and information, the number of Covid-19 cases it turned out 9% lower. This figure is the result of an average calculated on all the villages, both those in which the citizens used surgical masks and those who preferred cloth ones. This in no way means that the masks are only 9% effective – by the way only 42% of people used them – but which, together with other measures and education on the subject, these presidia have helped avoid a good number of infections. As the authors point out and as an article on Nature, which underlines the extension and validity of the work, no tests for Sars-Cov-2 have been carried out, so the fewer cases could be more.
Passed surgical masks, of failed cloth
Then looking only at the villages that have received surgical masks, the drop in infections is 11%. In particular, the favorable outcome can be seen more in the over 50s, who are also more often affected by symptomatic infections: the decrease is 23% between the ages of 50 and 60 e 35% over 60. While in the villages that have adopted those of cloth it is on average only 5%.
Also after 10 washes, the surgical ones still filter 76% of the smallest particles (those suspended via aerosol) against 95% before washing. While the cloth masks they had a filtering capacity from the start only 37%.
All masks were made in Bangladesh. The surgical ones consisted of 3 layers al 100% di polypropylene non-woven fabric, those of fabric from an outer layer of 100% polypropylene non-woven fabric and 2 layers of 60% cotton and 40% polyester in woven knit fabric.