An interesting preprint in medRxiv published by Melo and others posted on June 27th 2021 shows the effectiveness of facemasks in blocking the transmission of SARS-CoV-2. 

In 2019, SARS-CoV-2 transmitted via the airborne route caused the COVID-19 pandemic. 

It is still debated whether the use of masks can prevent transmission of SARS-CoV-2 and no study has evaluated the virus blocking efficacy of masks used by patients.  

This preprint looks at the evaluation of the efficacy of masks used by SARS-CoV-2 infected individuals.  

Masks used and nasopharyngeal swab samples were obtained from these patients. 

45 paired samples of nasopharyngeal swabs and masks were obtained and processed the majority of the masks were woven.  

Viral RNAs were amplified using a quantitative reverse transcription PCR reaction and detected only on the inner parts of masks.  

Median cycle threshold values of swabs from masks were 28.41 and 37.95, respectively.  

Statistically, there was a difference of approximately 10 CT values between swabs and masks and no significant difference in CT values amongst different types of masks.  

There were statistically significant differences in CT values between men and women and symptomatic and asymptomatic patients.  

The findings of this preprint suggested the blocking of the transmission of viruses by different types of masks and reinforcing the use of mask by both infected and non-infected individuals.  

Viral RNA was detected only on the inner part of the masks, i.e. that part which was in contact with the face.  

None of the masks were positive for RNA on the outer part, i.e. that part which is in contact with the external environment. 

The results of this study reinforce the evidence that in general, wearing masks will be beneficial to the community and that this beneficial effect is derived from the ability of masks to block the exhalation and inhalation of infectious viruses, regardless of the type of mask used. 

This study shows that it is important to use masks if you are infected with SARS-CoV-2 and also shows that different types of mask help to block viral transmission.  

The findings reinforce the importance of using masks as a preventative measure against viral transmission, regardless of the type of mask used, in addition to social distancing and personal hygiene measures.  

LGP, the leading London doctors’ clinic in Harley Street continues to emphasise the need to wear a mask in situations where social distancing is unable to be managed.

Dr Paul Ettlinger

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