While the link between excess winter mortality and winter respiratory diseases in the elderly is well described, the impact of the epidemic of influenza in the elderly is mainly assessed in France through specific surveillance in the general population. Syndromic surveillance data enables to monitor ED attendances and hospitalizations for various diagnostic codes groupings throughout the influenza epidemic, some of which often cited as influenza proxies, such as cardiorespiratory diagnostic groups.
In mainland France, the 2014-15 season was characterized by an intense influenza epidemic in the community (sub-type A(H3N2) dominant virus). Hospital overcrowding was early reported, partly linked to serious clinical presentations among the elderly, and leading to the triggering of a national emergency plan.
We hypothesized that ED numbers of clinical influenza cases underestimate the influenza burden among patients aged 65 years and over, especially when a A(H3N2) influenza subtype circulates.
Objective
To estimate the real burden of influenza epidemic on emergency departments (ED) attendances and hospitalizations among patients over 65 years in order to better understand determinants of overcrowding and mortality excess.