The 1997-98 influenza A epidemic in British Columbia

摘要: Active surveillance of influenza-like illness (ILI) in British Columbia has been routinely conducted from October to May each year. During the 1997–98 season, the influenza A/H3N2/Sydney/05/97-like strain was the predominant pathogen circulating in BC. This strain was not included in the influenza vaccine recommended by the World Health Organization. The surveillance program and the investigation of ILI outbreaks allowed Epidemiology Services at the BC Centre for Disease Control to measure the impact of a new and unexpected influenza virus in the community and to assess the effectiveness of vaccination and outbreak management in health-care facilities. Sentinel physicians documented increased influenza-like illness (ILI) activity when compared with the past 7 years. One hundred twenty-five elementary schools reported absenteeism greater than 10% due to ILI, representing over 5000 ill children. ILI outbreaks were identified in 62 health-care facilities; 1898 (31%) of 6108 residents were affected. There were 141 known deaths and 109 known hospitalizations associated with these outbreaks. Twenty-eight (46%) health-care facilities reported amantadine use for outbreak management. An increased risk of death was observed in health-care facilities that reported no amantadine use. A total of 76.5% of the residents in the health-care facilities were reported vaccinated. Non-vaccinated residents were approximately twice as likely to become ill, to be hospitalized due to ILI complications, or to die. Overall vaccine effectiveness for cumulative illness was 46%. Staff vaccination rate was low with a median of 24% vaccinated. Our findings …