Small study questions efficacy of cotton, surgical masks at stopping spread of SARS-CoV-2
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Surgical and cotton masks were ineffective at preventing the dissemination of SARS-CoV-2, the virus that causes COVID-19, according to a research letter published in Annals of Internal Medicine.
Researchers recruited four patients from South Korea with COVID-19. Two of the patients had upper respiratory infections: one had pneumonia and the other had pneumonia with acute respiratory distress syndrome. The age of the patients ranged from 35 to 82 years. Two of the patients were women.
Patients were asked to cough five times into a petri dish without wearing a mask, while wearing a disposable surgical mask, while wearing a reusable cotton mask and again without wearing a mask. Specimens from the outer surface and inner surfaces of the masks were collected via an aseptic swab.
At baseline, the patients’ median viral load of the nasopharyngeal sample was 5.66 log copies/mL and of the saliva samples was 4 log copies/mL. According to researchers, after coughing, the patients’ median viral load without a mask was 2.56 log copies/mL, with a surgical mask was 2.42 log copies/mL and with a cotton mask was 1.85 log copies/mL.
While most swabs from the inner mask surfaces were negative for SARS-CoV-2, all the swabs from the outer surfaces of the masks were positive for SARS-CoV-2, according to researchers.
“We are not sure as to whether the masks shortened the distance of viral particle transmission,” Sung-Han Kim, MD, PhD, chief of the office for infection control at Asan Medical Center in Seoul, South Korea, and a co-author of the Annals of Internal Medicine report, told Healio Primary Care. “Further studies are needed for cotton and surgical masks’ use in routine activities such as talking. Masks with high filtration efficiencies should also be tested in this regard.”
Kim added that the protective effect of N95 respirators or their equivalent are “likely the strongest,” but further research should be conducted to test this assertion. – by Janel Miller
Disclosures: The authors report no relevant financial disclosures.
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Peter Chin-Hong, MD
I am unmoved by these findings. I would still — 100% — encourage wearing surgical masks in most (non-aerosol generating) health care worker contexts. These findings will have zero impact on my practice.
These researchers did not simulate a real-life scenario. Finding something microbiologically is not equivalent to clinical reality. We know from human transmission data — not simulated data gleaned from smearing masks — that there was no transmission of COVID-19 when health care professionals wore surgical masks in front ofCOVID-19 patients. And among the general public, any mask is better than no mask, particularly in environments such as public transportation where it is difficult to maintain social distance.
Infection in humans is not about finding a bug. If patients sprayed their skin right now [with a virus], they would likely find those viruses, but that does not mean that they are going to become sick. I challenge investigators to find instances of human transmission from microbiological phenomena.
Reference: Ng K, et al. Ann Intern Med. 2020.doi:10.7326/L20-0175.
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