Year Cases per 100,000 1990 0 1991 0 1992 0 1993 0 1994 0 1995 0 1996 0.1 1997 0.2 1998 0.5 1999 1.1 2000 2.3 2001 4.1 2002 5.7 2003 7 2004 7.8 2005 8.3 2006 8.7 2007 9