Year Cases per 100,000 1990 23.2 1991 38.6 1992 60.2 1993 92 1994 136.7 1995 194 1996 262.1 1997 337.7 1998 416.1 1999 529.5 2000 624.8 2001 722.3 2002 788.7 2003 857.4 2004 900.8 2005 914.3 2006 938.1 2007 962