As the U.S. sees a nationwide spike in coronavirus cases, the Centers for Disease Control released new mask guidance.
The latest update says wearing a face covering doesn't just protect the people around you, but it also protects the wearer from incoming virus projectiles.
Originally, the CDC pushed the use of face masks to reduce the emission from virus-laden asymptomatic or presymptomatic infected wearers who feel well and may be unaware of their infectiousness to others.
Now, the CDC has added to that guidance, saying masks also reduce inhalation of those droplets by the wearer.
The CDC recommends individuals wear specifically non-valved multi-layer cloth masks.
Studies show cloth masks can both block up to 50-70% of fine droplets and particles and limit the forward spread of those that are not captured. Upwards of 80% blockage has been achieved in human experiments that have measured blocking of all respiratory droplets, with cloth masks in some studies performing on par with surgical masks as barriers for source control.
Multiple layers of cloth with higher thread counts have demonstrated superior performance compared to single layers of cloth with lower thread counts, in some cases filtering nearly 50% of fine particles for the wearer, studies show.
The CDC says some materials work better than others. For example, some materials like polypropylene may enhance filtering effectiveness, and other materials like silk may help repel moist droplets and reduce fabric moisture, maintaining breathability and comfort.
One of many "real-world" examples highlighted in the release details an investigation of a high-exposure event, in which two symptomatically ill hair stylists interacted with 139 clients.
The CDC says they interacted with each client for an average of 15 minutes during an eight-day period. They found that none of the 67 clients who consented to an interview and testing developed infection.
So what prevented the spread? The stylists and all clients universally wore masks in the salon as required by local ordinance and company policy at the time.