They've included midterms in that list, so that means every other year is an election year. And the dates are wrong!

SARS was late 2002 to 2004 with the bulk of it being in 2003.
Avian was around for years but worst in 2007
Swine flu was 2009 predominantly tailing off in 2010. The Wiki page for its outbreak is even called "2009 flu pandemic"
Zika was 15 to 16

All it really shows is there's frequently epidemics, not that they're exceptionally in election years.