Likely to spread and cause an epidemic disease:
— Plaguey fevers.

synonyms: pestiferous, pestilent, pestilential.

Causing irritation or annoyance:
— A plaguey newfangled safety catch.

synonyms: annoying, bothersome, galling, irritating, nettlesome, pesky, pestering, pestiferous, plaguy, teasing, vexatious, vexing ... show more.

In a disagreeable manner:
— It's so plaguey cold!.

synonyms: plaguily, plaguy.