infestation
  群襲,出沒,橫行
  in·fes·ta·tion /ˌɪnˌfɛsˈteʃən/ 名詞
  侵擾,侵襲,感染
  In·fes·ta·tion n.  The act of infesting or state of being infested; molestation; vexation; annoyance.
     Free from the infestation of enemies.   --Donne.
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  infestation
       n 1: the state of being invaded or overrun by parasites
       2: a swarm of insects that attack plants; "a plague of
          grasshoppers" [syn: plague]