Synonyms for Pestilence (same or very similar meaning)
WordNet sense 1 (a serious (sometimes fatal) infection of rodents caused by Yersinia pestis and accidentally transmitted to humans by the bite of a flea that has bitten an infected animal):
pest, plague, pestisWordNet sense 2 (a pernicious and malign influence that is hard to get rid of):
cankerFrom the ODE community, based on WordNetadd/edit