Effectiveness of Newly Applied Infection Control Policies to Suppress the Number of Cases with Hospital-acquired Influenza Infection at Iwate Medical University Hospital

Iwate Medical University Hospital (IMUH) is a general regional hospital with approximately 1,000 beds and emergency facilities. Due to the increased prevalence of cases of hospital-acquired influenza during the 2004/5 epidemic season, measures to systematically and comprehensively prevent the spread of seasonal influenza such as reinforcement of the active surveillance of influenza and adequacy of patient placement and the introduction of a new zoning system based on transmission-based precautions, were implemented. This report compares pre-and post intervention, and analyzes the impact on the prevalence of hospital-acquired influenza patients. Comparison of the prevalence of the 2005/6 season and 2004/5 season, irrespective of the fact that patients with influenza upon admission to the hospital doubled from 9 patients to 18, the number of influenza patients assumed to have secondary infections within the hospital markedly decreased from 48 to 20. In the 2004/5 season, a significant correlation was seen between the increase in the number of community-acquired influenza infections and the number of hospital-acquired ones. In contrast, no significant relationship was seen in the 2005/6 season. To exclude any influence due to seasonal differences in influenza epidemics, the secondary infection rate index one showed a decrease from of 36.8% to 23.7%. Based on the above results, influenza measures at IMUH in the 2005/6 season are considered to have suppresses the number of secondary infections occurring within the hospital.