Outbreak of invasive Group A streptococcus disease in a nursing home in Ireland in February 2023 caused by type 18.

An out-of-season increase in cases of invasive Group A streptococcus (iGAS) was observed in Ireland between October 2022 and August 2023. We describe the management of an iGAS outbreak involving three nursing home residents in Ireland in early 2023. A regional Department of Public Health was notified of an iGAS case in a nursing home resident in January 2023. When two further cases among residents were notified 7 days later, an outbreak was declared. Surveillance for GAS/iGAS infection in residents and staff was undertaken. The site was visited to provide infection prevention and control (IPC) support. Isolates were typed. A total of 38 residents and 29 staff in contact with resident cases were provided with antibiotic chemoprophylaxis. Seven additional staff with no direct resident contact also received chemoprophylaxis after finding one probable localised GAS infection among them. No more iGAS cases subsequently occurred.Site visit recommendations included advice on terminal cleaning and cleaning of shared equipment, as well as strengthening staff education on hand hygiene and masking. All isolates were of subtype 18.12, a subtype not previously detected in Ireland. Key outbreak control measures were rapid delivery of IPC support and chemoprophylaxis. 18 is infrequently associated with GAS infections.