"he must be sick" in German He must be sick. Er muss krank sein. Detailed translations for "he must be sick" He must be sick. He must be sick. Er muss krank sein. - He must be sick. Source: opensubtitles.org Corpus by OPUS Request review - Er muss krank sein. He must be sick. Source: opensubtitles.org Corpus by OPUS Request review Er muss krank sein.