 prolonged silent carriage genomic virulence potential and transmission between staff and patients characterize a neonatal intensive care unit nicu outbreak of methicillin resistant staphylococcus aureus mrsa an outbreak of mrsa in a nicu was investigated in california healthcare personnel were identified as a potential key link in transmission and colonization whole genome sequencing wgs further identified circulation of a highly virulent outbreak strain for at least 7 months prior to outbreak recognition 