Our study revealed that abnormally high levels of airborne A. fumigatus conidia correlated with new cases of IA, even in patients who were not severely immunocompromised. The demonstration of matches between air and clinical genotypes reinforces the role of environmental air in the acquisition of IA during the period following MHS. Environmental monitoring of Aspergillus spores in the air of postoperative units is mandatory, even when these units receive nonimmunocompromised patients undergoing major surgery.