The Effect of Mask Use on Seasonal Virus Diversity in SARS CoV-2 Negative Patients Treated as Inpatients During the 2021–2022 and 2022–2023 Seasonal Flu Period

The study aimed to explore the protective effect of mask use against respiratory tract viral agents during the pandemic. The study included patients with a COVID-19 negative test who were hospitalized in the pulmonary disease clinic with the diagnoses of asthma attack, chronic obstructive pulmonary disease (COPD) exacerbation, and pneumonia in two periods: during mandatory mask use (October 2021 - May 2022) and after the mask mandate was lifted (October 2022 - May 2023). Combined nose and throat swab samples taken from the patients were evaluated for viral agents by using the PCR test method. Viral agents isolated from the patients in the two periods were compared based on hospitalization diagnoses and periods. The study enrolled 1,335 patients, 483 female and 852 male. It was found that viral agents significantly increased during the period without a mask mandate compared to the period when the mask mandate was in effect (41.6% vs. 23.4%) (<i>p</i> < 0.001). During the period without mask mandate, influenza A, H1N1, and RSV/AB viruses significantly increased (<i>p</i> = 0.019, <i>p</i> = 0.003, <i>p</i> < 0.001, respectively). Our results indicated that mask use during the pandemic is protective against the transmission of respiratory tract viruses. Thus, it can be concluded that mask use is important not only in the coronavirus pandemic but also especially in influenza and RSV epidemics.