Year	Cases per 100,000
1980	4
1981	3
1982	4
1983	4
1984	3
1985	3
1986	2
1987	42
1988	3
1989	3
1990	4
1991	6
1992	15
1993	6
1994	7
1995	18
1996	20
1997	22
1998	20
1999	18
2000	16
2001	16
2002	16
2003	16
2004	16
2005	16
2006	14
2007	13