Influenza monitoring in the Swiss Sentinel Surveillance Network

In Switzerland, the monitoring of influenza-like illness (ILI) is mainly performed by the Swiss Sentinel Surveillance Network, run by the Swiss Federal Office of Public Health (SFOPH), the University of Berne, and the National Centre of Influenza (NCI). In 2003, 240 general practitioners, physicians specialized in internal medicine, and pediatricians voluntarily reported weekly morbidity data-covering about 3.5% of consultations in primary health care. Reporting of ILI follows a case definition. Reports include data on age, sex, the presence of pneumonia, hospitalization, mortality, vaccination status, and therapy. Influenza immunization is also reported and includes data on sex, age, initiative, and reasons for vaccination. Samples for the subtyping of influenza viruses are sent to the National Reference Centre of Influenza. During the past 4 years, about 55% of the sentinel physicians have been conducting a near patient rapid test for the detection of Influenza A and B. For the past 10 winter seasons, the life span of influenza epidemics ranged from 4 to 13 weeks (average 9.9 weeks, median 10 weeks). At the peak of the epidemics, the number of ILI reports ranged from 3.23 to 9.26 cases per 100 medical contacts (MC) per week (average 5.91, median 5.58). The Swiss Sentinel Surveillance Network is an efficient instrument for monitoring influenza. (C) 2004 Published by Elsevier B.V.