Clinical incidence rate of influenza-like illness (ILI) per 100,000 population recorded by the Royal College of General Practitioners Weekly Returns Service.

<p>Weekly incidence rate of ILI presented for all-age, 0–4 and 5–14 years age groups. Vertical shaded bars represent defined periods of influenza virus circulation derived from laboratory reports.<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0007671#pone.0007671-Fleming3" target="_blank">[8]</a> Arrows indicate those years in which a new variant was introduced into the community (1. A/Wuhan/359/95; 2. A/Sydney/5/97; 3. A/Fujian/411/02).