Effectiveness of face masks in blocking the transmission of SARS-CoV-2: A preliminary evaluation of masks used by SARS-CoV-2-infected individuals

  1. Vinicius M. Mello
  2. Cristiane M. Eller
  3. Andreza L. Salvio
  4. Felipe F. Nascimento
  5. Camila M. Figueiredo
  6. Emanuelle S. R. F. Silva
  7. Paulo S. F. Sousa
  8. Pamela F. Costa
  9. Anne A. P. Paiva
  10. Maria A. M. M. Mares-Guias
  11. Elba R. S. Lemos
  12. Marco A. P. Horta

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Abstract

In 2019, a novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is transmitted via the airborne route, caused a new pandemic namely, “coronavirus disease 2019” (COVID-19). Although the effectiveness of face masks to prevent the transmission of SARS-CoV-2 is debated, no study has evaluated the virus-blocking efficacy of masks used by patients. We aimed to evaluate this efficacy of masks used by SARS-CoV-2-infected individuals. Data, masks used, and nasopharyngeal swab samples were obtained from these patients. Forty-five paired samples of nasopharyngeal swabs and masks were obtained and processed; the majority of masks were woven. Viral RNAs were amplified using quantitative reverse‐transcription polymerase chain reaction and detected only on the inner parts of masks. Median viral load (VL) values of swabs and masks were 1.954x10 6 and 2,51x10 3 , respectively. Statistically, there was a difference of approximately 1000 RNA copies/mL between swabs and masks and no significant difference in VL values among different types of masks. There were statistically significant differences in VL values between men and women and between symptomatic and asymptomatic patients. Our findings suggest the blocking of virus transmission by different types of masks and reinforce the use of masks by both infected and non-infected individuals.

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  1. Version published to 10.1371/journal.pone.0264389
  2. ScreenIT

    SciScore for 10.1101/2021.06.20.21259167: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    EthicsIRB: Ethics Statement The Oswaldo Cruz Institute/IOC/FIOCRUZ Research Ethics Committee approved this study (
    Consent: All patients who were included in the study agreed with their participation in the research by signing the informed consent. 2.2. Study Population and Sample Collection Nasopharyngeal swab samples and masks were collected (between December 2020 to March 2021) from patients who were suspected to be infected by SARS-CoV-2 and attended the Municipal Theatre and Benjamin Constant Institute survey, conducted in the city of Rio de Janeiro, Brazil, according to medical decision and after obtaining permissions from the patients.
    Field Sample Permit: After sampling, the nasopharyngeal swab was inserted into a vial containing 3 mL of a viral transport medium (VTM; Xpert nasopharyngeal sample collection kit, Cepheid, Sunnyvale, CA, USA).
    Sex as a biological variable) Masks Ct IQR P-value Swab Ct IQR P-value Sex 0.01 0.02 Female 20 (44.4) 34.54 (28.69–40.00) 24.87 (20.5–28.45) Male 25 (55.6) 40.00 (28.69–40.00) 31.47 (23.97–32.84
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.

    Table 2: Resources

    No key resources detected.

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    This was a preliminary study and has some limitations. The sample size was relatively small, and it did not evaluate the filtering efficiency of the masks as performed in some other studies [28,29]. Furthermore, this study only evaluated masks from SARS CoV 2 infected individuals with a positive qRT-PCR. Further studies are needed to evaluate the masks of uninfected individuals who have direct contact with infected individuals. Further studies, including a larger number of masks, are also needed to analyze the viability of the virus detected in infected masks through cell culture. However, our results provided real-life evidence regarding blocking of viral transmission by masks used by individuals infected by SARS-CoV-2. Furthermore, the results also reinforce the suggestion to use a mask by everyone, regardless of whether the individual is infected or not. This is important since there are asymptomatic cases of infection and evidence of transmission of the virus even before the appearance of the first symptoms, as reported by some studies [38,41].

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    Results from scite Reference Check: We found no unreliable references.

    About SciScore

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  3. Version published to 10.1101/2021.06.20.21259167v2 on medRxiv
  4. Version published to 10.1101/2021.06.20.21259167v1 on medRxiv