A new systematic review examined 125 reported outbreaks between 1995 and 2023, looking at both the factors that contributed to them and the measures used to bring them under control (Gao et al., 2026).

Most outbreaks occurred in intensive care and neonatal units, with carbapenem-resistant and Gram-negative bacteria presenting the greatest threat. The review found that outbreaks were shaped by interacting pressures, including invasive procedures, overstretched systems and persistent environmental reservoirs.

Containment was also consistently multi-modal. Contact isolation and hand hygiene appeared in every outbreak response, often alongside staff training, environmental cleaning, microbiological typing, antimicrobial stewardship, equipment management and environmental surveillance. For the most difficult outbreaks, ward closure was sometimes required.

The practical lesson for Infection Prevention and Control teams is that identifying connected patients is only part of the investigation. Teams also need to understand what may be driving an outbreak so they can target the response. An environmental reservoir may require a different investigation from transmission linked to patient transfers or gaps in screening.

For NEX, this points towards a longer-term opportunity: moving from showing possible transmission links to helping teams assess likely outbreak drivers and identify the most relevant actions. The review cannot establish the independent effect of each intervention, but it reinforces an important principle. Effective outbreak control depends on bringing together multiple forms of evidence and acting on them as a system.