Year Cases per 100,000 1990 0 1991 0 1992 0 1993 0 1994 0 1995 0 1996 0 1997 0 1998 0 1999 0 2000 0 2001 0.1 2002 0.2 2003 0.5 2004 1.1 2005 1.8 2006 2.5 2007 2.6