Risk of infection following a visit to the emergency department: a cohort study.

Background: The risk of infection following a visit to the emergency department is unknown. We explored this risk among elderly residents of long-term care facilities.
Methods: We compared the rates of new respiratory and gastrointestinal infections among elderly residents aged 65 years and older of 22 long-term care facilities. We used standardized surveillance definitions. For each resident who visited the emergency department during the study period, we randomly selected two residents who did not visit the emergency department and matched them by facility unit, age and sex. We calculated the rates and proportions of new infections, and we used conditional logistic regression to adjust for potential confounding variables.
Results: In total, we included 1269 residents of long-term care facilities, including 424 who visited the emergency department during the study. The baseline characteristics of residents who did or did not visit the emergency department were similar, except for underlying health status (visited the emergency department: mean Charlson Comorbidity Index 6.1, standard deviation [SD] 2.5; did not visit the emergency department: mean Charlson Comorbidity index 5.5, SD 2.7; p < 0.001) and the proportion who had visitors (visited the emergency department: 46.9%; did not visit the emergency department: 39.2%; p = 0.01). Overall, 21 (5.0%) residents who visited the emergency department and 17 (2.0%) who did not visit the emergency department acquired new infections. The incidence of new infections was 8.3/1000 patient-days among those who visited the emergency department and 3.4/1000 patient-days among those who did not visit the emergency department. The adjusted odds ratio for the risk of infection following a visit to the emergency department was 3.9 (95% confidence interval 1.4-10.8).
Interpretation: A visit to the emergency department was associated with more than a threefold increased risk of acute infection among elderly people. Additional precautions should be considered for residents following a visit to the emergency department.