February 9 In view of the stronger infectivity of the COVID-19 Variant strain, some American experts said that it is time to consider using medical-grade masks or surgical masks and cloth masks at the same time.
According to AFP on the 9th, there is increasing evidence that the tiny droplets generated by ordinary breathing and speech can be transmitted several meters away, which is one of the common modes of transmission of the novel coronavirus.
Later, more infectious Variant strains such as Variants appeared, which made the pandemic worse.
Compared with previous strains, Variant strains only need to have lower virus volumes to cause COVID-19 symptoms. The U.S. government initially advised people to cover their faces.
Due to the extreme shortage of suitable masks at that time, the U.S. government encouraged people to make their own masks with T-shirts or scarves, but these are far from ideal options.
“The function of masks depends on two things, filtering and tightness,” said Linsey Marr, a professor at Virginia Tech and State University.
She said that good filtration can remove as many particles as possible, and good density means that there are no loopholes around the side of the mask to let the air and viruses slip in.
The best materials to block micro particles include polypropylene nonwoven fabrics, N95 and many surgical masks, as well as these materials used in the high-efficiency air particle filter (HEPA) on aircraft.
As for the fabric, she thinks tight woven cotton works best. But she does not recommend wearing more than two layers of masks, because it will affect breathability and unfavorable breathing.
Ranu Dhillon, a global health expert at Harvard Medical School, has been advocating wearing better masks since last spring, but the lack of clear information in this regard has attracted public attention and disappointed him.
Relevant departments have not jointly promoted the mass production and distribution of high-specification masks.
University of Maryland professor Donald Milton also believes that it is very important to wear a better mask.
He and DeLion are cautiously optimistic that the U.S. government may soon include relevant matters as policy. CNN reported last week that the U.S. government has begun to plan the first batch of official mask standards.