Mucormycosis outbreak caused by Rhizomucor pusillus in a Hematopoietic Stem Cell Transplant Unit, Brazil.

An outbreak of mucormycosis caused by Rhizomucor pusillus occurred in a Brazilian HSCT unit, with four cases identified over ten months and three patients surviving.

• Why it matters: Mucormycosis has high mortality in immunocompromised patients, and healthcare-associated outbreaks are rare but pose significant risks, highlighting the need for outbreak investigation and control.
• What they did: The investigation involved screening hospital records, microbiological identification, ITS sequencing, WGS phylogenetic analysis, and environmental sampling, with cases classified per EORTC/MSGERC criteria.
• The result: Despite negative environmental findings and non-clonal isolates, epidemiological evidence suggests nosocomial transmission via the air system, and early diagnosis plus aggressive treatment led to favorable outcomes in most patients.