This is a bar graph showing the notification rate (per 100,000 population) of Ross River virus notifications from the Perth Metropolitan and Peel regions by month from January 1990 to June 2012. It shows a seasonal pattern of increased notifications from October to March each year with high notification rates in the summers of 2003/2004, 2005/2006 and 2012. It also shows less pronounced summer peaks from 2006 to 2009 inclusive.