Year	Cases per 100,000
1990	0
1991	0
1992	0
1993	0
1994	0
1995	0
1996	0
1997	0
1998	0.1
1999	0.6
2000	2
2001	3
2002	3.6
2003	4.3
2004	4.9
2005	5.6
2006	6.2
2007	6.9