All past 4 pandemics started with a mild outbreaks in the spring.

http://www.bloomberg.com/apps/news?pid=20601087&sid=aQFT.hrAp_5s
June 11 (Bloomberg) — Swine flu, causing mostly mild disease outbreaks on four continents, prompted the World Health Organization to declare the first influenza pandemic since 1968, according to a statement by the Swedish government.

Margaret Chan, the WHO’s director-general, moved to the top of the agency’s six-stage pandemic alert scale today on evidence the virus is spreading in communities outside the Americas. The new H1N1 flu strain has taken root in Australia, Chile, the U.K. and Spain since its discovery in Mexico and the U.S. in April.

The pandemic declaration confirms the fourth time in the last century a new influenza strain has swept across the globe. It’s the third time since April 27 that WHO has raised the alert level over swine flu, which has turned up in more than 70 nations as far removed as Iceland, New Zealand and the Bahamas.