Outbreaks in hematopoietic stem cell transplant units: a systematic review

To identify and present the pathogens and sources of contamination linked to outbreaks within hematopoietic stem cell transplant (HSCT) units.

Systematic review.

Inpatient HSCT units.

The PubMed/Medline databases were systematically searched as per the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines, employing the search terms "stem cell", "bone marrow", "transplant", "transplantation", "outbreak" and "pseudo-outbreak" from inception until July 31, 2024. Data on the type of event, pathogen involved, and source of contamination were extracted from eligible publications.

In total, 39 studies including 387 patients were included in this review. The overall mortality rate was 23%. Pathogens identified included adenovirus, RSV, Pseudomonas aeruginosa, Aspergillus spp., and non-tuberculous mycobacteria (NTM). P. aeruginosa outbreaks were associated with contaminated sanitary fixtures (P = .007) and water (P = .039), outbreaks caused by NTM were associated with water (P = .009), while Aspergillus spp. outbreaks were associated with construction (P < .001). An index case was identified in 36.8% of viral outbreaks (P = .016). Other sources included inadequate disinfection and transmission from visitors.

Our study highlights several associations between pathogens involved in HSCT unit outbreaks and their respective sources. Establishing standardized guidelines for unit construction - particularly for ventilation and water safety - could further reduce the risk of pathogen transmission and enhance infection prevention in these high-risk settings.