Investigation of a Group A Streptococcal Outbreak among Residents of a Long-Term Acute Care Hospital

Background. In January 2008, a long-term acute care hospital (LTACH) in New Mexico reported a cluster of severe group A Streptococcus (GAS) infections. Methods. We defined a case as illness in a patient in the LTACH from 1 October 2007 through 3 February 2008 from whom GAS was isolated from a usually sterile site or with illness consistent with GAS infection and GAS isolated from a nonsterile site. To identify carriers, we swabbed the oropharynx and skin lesions of patients and staff. We observed facility procedures to assess possible transmission routes and adherence to infection control practices. We also conducted a case-control study to identify risk factors for infection with use of asymptomatic patients who were noncarriers as control subjects. Results. We identified 11 case patients and 11 carriers (8 patients and 3 staff). No carriers became case patients. Significant risk factors for infection in univariate analysis included sharing a room with an infected or colonized patient (6 [55%] of 11 case patients vs 3 [8%] of 39 control subjects), undergoing wound debridement (64% vs 13%), and receiving negative pressure wound therapy (73% vs 33%). Having an infected or colonized roommate remained associated with case patients in multivariable analysis (odds ratio, 15.3; 95% confidence interval, 2.5-110.9). Suboptimal infection control practices were widespread. Conclusions. This large outbreak of GAS infection was the first reported in an LTACH, a setting that contains a highly susceptible patient population. Widespread infection control lapses likely allowed continued transmission. Similar to the situation in other care settings, appropriate infection control and case cohorting may help prevent and control outbreaks of GAS infection in LTACHs.