Year Cases per 100,000 2000 31 2001 28 2002 26 2003 25 2004 23 2005 21 2006 20 2007 19 2008 19 2009 18 2010 18 2011 17 2012 16 2013 16 2014 15 2015 14 2016 14 2017 13 2018 12 2019 11 2020 10