Seasonal variations in mold identification in medical microbiology laboratories using MSI-2 application, France (2020-2024)

Molds are ubiquitous environmental microorganisms with major implications for human health, ranging from allergic reactions to invasive infections. Although the environmental seasonality of several fungal spores has long been recognized, its reflection in clinical isolates remains poorly explored. A total of 218,682 fungal spectra generated by 97 medical microbiology laboratories across France between 2020 and 2024 were analyzed, based on identifications performed using the MSI-2 MALDI-TOF MS web platform. Seasonal patterns were assessed through additive decomposition, autocorrelation, and formal statistical testing. Distinct seasonal variation patterns were identified across taxa. Significant seasonality was detected for multiple taxa, including Alternaria, Cladosporium, Aspergillus sections Nigri and Flavi, Talaromyces, several taxa of Basidiomycota, and Rhizopus arrhizus. Positive or negative correlations between fungal identification counts and national mean temperature values were observed depending on the taxon. This study highlights the importance of considering seasonality in understanding the epidemiology of fungal diseases and demonstrates the value of multicenter MALDI-TOF MS data as a tool for epidemiological surveillance.