Executive Summary

Influenza is associated with illnesses such as pneumonia, other respiratory disease and congestive heart failure, and in severe cases leads to death (Fleming, 2000a; Nichol et al., 1998). To determine the effect on hospital admissions from influenza epidemics, estimates of hospital admissions for influenza and pneumonia (P&I), other respiratory diseases (ORC) and congestive heart failure (CHF) associated with influenza epidemics are required. Because hospital admissions for these conditions may occur in the absence of influenza, these hospital admissions are referred to as “excess hospitalisations”. That is, the hospital admissions that could be averted if an influenza epidemic could be prevented. Method Four age-groups (0-15 years, 16-50 years, 51-65 years and 66+) were modelled using Structural Time Series Models (STSM). Data from the Swiss Sentinel Surveillance Network on GP consultation rates for Influenza-like illness (ILI), and Swiss hospital admission data were obtained for 1987 to 1996. Dependant variables were the hospital admission rates for each of the age-groups for P&I, ORC, and CHF. The explanatory variable was the GP consultation rate for ILI plus a lag of one-week of this variable. A trigonometric season form with a stochastic component was used to account for potentia