A pseudo-outbreak of COVID-19 associated pulmonary aspergillosis: a microbiological investigation of both the patients and the environment.

Background: We experienced a pseudo-outbreak of aspergillosis in a newly constructed COVID-19 ward. Within the first 3 months from the commencement of the ward, six intubated patients of COVID-19 developed probable or possible pulmonary aspergillosis. We suspected an outbreak of pulmonary aspergillosis associated with ward construction and launched air sampling for the investigation of the relationship between these. Methods: The samples were collected at 13 locations in the prefabricated ward and three in the general wards, not under construction, as a control. Results: The results from samples revealed different species of Aspergillus from those detected by the patients. Aspergillus sp. was detected not only from the air samples in the prefabricated ward but also in the general ward. Discussion: In this investigation, we could not find evidence of the outbreak that links the construction of the prefabricated ward with the occurrence of pulmonary aspergillosis. It might suggest that this series of aspergillosis was more likely occurred from fungi that inherently colonized patients, and was associated with patient factors such as severe COVID-19 rather than environmental factors. Once an outbreak originating from building construction is suspected, it is important to conduct an environmental investigation including an air sampling.