WordNet sense 1 (likely to spread and cause an epidemic disease):

pestiferous, pestilent, pestilential

WordNet sense 2 ((especially of medicine) of disease or anything resembling a disease; attacking or affecting many individuals in a community or a population simultaneously):

epidemic

WordNet sense 3 (in a disagreeable manner):

plaguily, plaguy

WordNet sense 4 (causing irritation or annoyance):

annoying, bothersome, galling, irritating, nettlesome, pesky, vexatious, pestering, teasing, vexing

WordNet sense 5 (not to your liking):

disagreeable