Year Cases per 100,000 1990 0 1991 0 1992 0 1993 0 1994 0 1995 0.1 1996 0.5 1997 1.4 1998 2.3 1999 3 2000 3.8 2001 4.7 2002 5.8 2003 6.8 2004 7.8 2005 9.3 2006 9.8 2007 10.3