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Environmental and Phylogenetic Investigations of Aspergillus flavus Outbreak Linked to Contaminated Building Materials, Denmark, 2025
Journal article   Open access   Peer reviewed

Environmental and Phylogenetic Investigations of Aspergillus flavus Outbreak Linked to Contaminated Building Materials, Denmark, 2025

Alexander Gewecke, Raphael Niklaus Sieber, Soren Hallstrom, Marc Stegger, Barbara Kolarik, Jenny D. Knudsen, Birgitte Andersen, Astrid Hall, Nadja Hawwa Vissing and Maiken Cavling Arendrup
Emerging infectious diseases, Vol.32(3), pp.376-387
2026
DOI: https://doi.org/10.3201/eid3203.251219
PMID: 41863515
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Open Access CC BY V4.0

Abstract

Immunology Infectious Diseases Life Sciences & Biomedicine Science & Technology
An Aspergillus flavus outbreak occurred in a tertiary hospital in Denmark. We compared environmental sampling methods, investigated the outbreak through short tandem-repeat genotyping, STRAfla, and analyzed isolate phylogeny using whole-genome sequencing. Paired sampling revealed that air sampling underestimated A. flavus burden (8 CFU/81 air samples vs. 585 CFU/81 surface samples), and culturing at 37 degrees C was superiorto 25 degrees C (risk ratio 1.77; p<0.001). STRAfla (n = 145) confirmed clonality of the outbreak isolates. Active growth was identified in a kitchen inside the affected ward. Genetically related isolates were also found in the Department of Clinical Microbiology and in 4 unrelated wood-based building materials from retailers in Denmark. Phylogenetic analyses of 167 isolates supported introduction of A. flavus from building materials. We hypothesize that water damage enabled germination of dormant spores in precontaminated wood-based products. Our findings highlight a risk factor for outbreaks and should inform future hospital construction and infection prevention strategies.

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