Face mask use and viral load in patients with mild symptoms of COVID-19

Objective: Previous studies indicated that face masks reduce the probability of infection by SARS-CoV-2 but did not examine the relationship between SARS-CoV-2 viral load and mask usage. This study analyzed this relationship.

Methods: This cross-sectional study evaluated patients admitted to a public Emergency Care Unit in Belo Horizonte, MG, Brazil, between October 2020 and March 2021. Convenience samples were recruited during the study period. Adult patients with COVID-19 symptoms were invited to participate after being examined by a physician according to the Emergency Care Unit routine. This study included 441 adults with mild symptoms diagnosed with COVID-19 via RT-PCR, who were tested until the 14th day after symptom onset. Participants were interviewed about mask usage, oropharyngeal swabs were collected, and the SARS-CoV-2 viral load was measured using RT-PCR. The difference between the SARS-CoV-2 viral load in the groups of individuals who regularly used and did not use masks was subjected to a hypothesis test.

Results: Of the patients who had swabs collected 1-5 days after symptom onset, 64.9% of those not using masks regularly and 45.5% of those using masks regularly presented a high SARS-CoV-2 viral load. This difference was statistically significant (p=0.0073). Considering only the patients who had swabs collected 4-8 days after symptom onset, 44.1% of those not using masks regularly and 30.8% of those using masks regularly presented a high SARS-CoV-2 viral load; this difference was statistically significant (p=0.0364).

Conclusion: When people who regularly wear a face mask contract COVID-19, they have a significantly lower probability of having a high viral load of SARS-CoV-2 compared to those who do not regularly wear masks.