Table 1. Begin and end of the period of influenza circulation per season based on virological data collected by the NRCI, Germany.

season	begin	end	duration [in weeks]
2001/02	2002 w 04	2002 w 15	12
2002/03	2003 w 04	2003 w 15	12
2003/04	2003 w 51	2004 w 14	16
2004/05	2005 w 02	2005 w 14	13
2005/06	2006 w 07	2006 w 17	11
2006/07	2007 w 02	2007 w 15	14
2007/08	2007 w 52	2008 w 17	18
2008/09	2008 w 49	2009 w 15	19
2009/10	2009 w 42	2010 w 04	16
2010/11	2010 w 50	2011 w 14	17