noun, noun or participle which takes 'suru', intransitive verb, noun which may take the genitive case particle 'no'
big craze; boom; huge popularity
Used for fads, trends, or things that become explosively popular in society.
このゲームは今、世界中で大流行している。
This game is now a huge craze all over the world.
That song is showing signs of becoming a massive hit.
noun, noun or participle which takes 'suru', intransitive verb, noun which may take the genitive case particle 'no'
widespread contagion; large outbreak
Used for infectious diseases spreading widely. Often appears in news or medical contexts.
新型インフルエンザの大流行が懸念されている。
A large outbreak of the new influenza is feared.