Influenza. The role of burden-of-illness research.

Influenza is associated with a significant economic burden on both society and the individual, resulting in considerable healthcare costs and loss of productivity, as well as intangible costs such as suffering, grief and social disruption. The incidence and severity of influenza infection depend, at least in part, on the age and health status of the population. For example, the incidence of influenza is relatively high among children and young adults, but serious complications are much more likely to occur among the very young (< 1 year of age) and the elderly (> 65 years of age). School absenteeism tends to peak in the first half of a typical 6- to 8-week influenza epidemic, followed by workplace absenteeism in the latter half as school-aged children pass the infection to family members. Cost-of-illness studies are used by policy-makers to justify budgets and set priorities for prevention programmes, research and other expenditures. On the basis of German Sickness Fund data, recent estimates indicate that the cost of an influenza epidemic in that country is approximately 2 billion Deutschmarks (approximately $US1.4 billion). The bulk of these costs reflects indirect costs associated with lost productivity, a finding also noted in an earlier French cost-of-illness study of influenza. Thus, the main economic burden of influenza falls on infected individuals, their employers and their relatives. Methodology used in cost-of-illness studies can be quite variable. For example, two main approaches are used in measuring indirect costs (human capital and willingness to pay), although there is controversy as to which is the preferred method. Thus, investigators involved in cost-of-illness studies must be explicit regarding study methodology in order to allow for appropriate interpretation of study results by interested parties.