It is widely thought that during respiratory viral infection, face masks may prevent transmission of the virus. Do face masks worn by patients with coronavirus disease- 2019 (COVID-19) prevent contamination of the environment? There are uncertainties in the very limited studies on this topic.
Researchers from University of Ulsan College of Medicine and Sejong University, South Korea observed that a previous study found that surgical masks and N95 masks were equally effective in preventing the dissemination of influenza virus and so surgical masks might help prevent transmission of severe acute respiratory syndrome–coronavirus 2 (SARS–CoV-2). However, COVID-19 pandemic led to shortages of both N95 and surgical masks, and cotton masks have gained interest as a substitute. In that context, the researchers carried out a simple and mostly realistic study to evaluate the effectiveness of surgical and cotton masks in filtering SARS–CoV-2.
They compared disposable surgical masks (180 mm × 90 mm, 3 layers [inner surface mixed with polypropylene and polyethylene, polypropylene filter, and polypropylene outer surface], pleated, bulk packaged in cardboard; KM Dental Mask, KM Healthcare Corp) with reusable 100% cotton masks (160 mm × 135 mm, 2 layers, individually packaged in plastic;
Four patients, two males and two females (aged 35, 61 and 62, 82 years respectively) suffering from COVID-19 participated in the study. The researchers instructed them to cough 5 times each onto suitably arranged petridishes at approximately 20 cm from the patients’ mouths while wearing the following sequence of masks: no mask, surgical mask, cotton mask, and again with no mask. They used a separate petri dish for each of the 5 coughing episodes. The researchers swabbed with aseptic Dacron swabs, the outer and inner surfaces of the surgical and cotton mask in a specific order. The researchers evaluated the viral loads separately. They also estimated the median viral loads of nasopharyngeal and saliva samples from the 4 patients.
After careful evaluation, the researchers concluded that “both surgical and cotton masks seem to be ineffective in preventing the dissemination of SARS–CoV-2 from the coughs of patients with COVID-19 to the environment and external mask surface”.
In a paper published in Annals of Internal Medicine on April 6, 2020, the researchers described their study, explained its results and limitations and reviewed the results of the earlier studies.
The original paper is available at https://annals.org/aim/fullarticle/2764367/effectiveness-surgical-cotton-masks-blocking-sars-cov-2-controlled-comparison