plague

[1]	badger , harry , hound , pester , annoy , vex , irritate , bother , harass , nag , nettle , exasperate , gall , annoy , irk , torment , torture , anguish , distress , (Brit) chivvy/chivy/chevy
[2]	blight
[3]	harass , hassle , harry , chivy , chivvy , chevy , chevvy , beset , molest , provoke

[1]	scourge , pestilence , pest , epidemic , pestilence , pestis , affliction , pandemic , calamity , curse , evil , bane , blight , visitation
[2]	irritation , pestilence , pest , annoyance , nuisance , pest , vexation , bother , thorn in one's side/flesh , torment , torture , (Colloq) pain (in the neck) , headache , aggravation , (Slang) drag , bitch , hassle , (Colloq) (Slang) pain in the (Brit) arse/(US) ass
[3]	infestation