Environmental Mold Management in Negative-Pressure Isolation Wards During the COVID-19 Pandemic: A Potential Indicator of COVID-19-Associated Pulmonary Aspergillosis

Abstract

High concentration of mold spores in inhaled air is an important risk factor for invasive mold infections. COVID-19 (coronavirus disease 2019)-associated pulmonary aspergillosis (CAPA) is a serious complication of severe COVID-19. To investigate the mold distribution in negative-pressure isolation wards and its potential association with CAPA incidence, we conducted microbiological air sampling and retrospectively analyzed CAPA cases in a tertiary care hospital in Korea during the COVID-19 pandemic. Air sampling was conducted in January 2022 at multiple sites in four negative-pressure isolation wards designated for managing severe COVID-19 patients. A portable microbial air sampler (MAS-100 NT) was used for air sampling, and Tryptic Soy Agar plates were incubated to identify mold isolates at the genus level. CAPA cases (January 2021–June 2023) were defined by antifungal treatment, mycological evidence (serum galactomannan index > 0.5), and radiological findings. Immunomodulator use, including dexamethasone and tocilizumab, was analyzed to identify clinical risk factors influencing CAPA incidence. Among the isolated molds, Aspergillus (86.7%) was the most prevalent, followed by Penicillium (53.3%), Mucorales (20%), and Paecilomyces (13.3%). Mold concentrations were highest in areas adjacent to a construction site. Intervention procedures, including installing air purifiers and reinforcing seals between the adjoining construction site and isolation ward, effectively reduced mold concentrations and paralleled a decline in CAPA incidence. While increased foot traffic after the relaxation of COVID-19 restriction measures led to a rise in spore concentration, the incidence of CAPA did not increase, likely due to the decreased use of immunomodulators such as corticosteroids and tocilizumab. Construction-related mold spore increases can be mitigated with appropriate interventions, and pedestrian traffic near isolation wards may need regulation. Monitoring and mitigating environmental mold contamination are crucial to preventing opportunistic respiratory mold infections in negative-pressure isolation wards and should be interpreted in conjunction with clinical risk factors.