Bad news circulates quickly (because people are apt to hear it and then share it with others). A: "How does the whole school already know that I got suspended?" B: "Well, bad news travels fast."
Prov. Information about trouble or misfortune disseminates quickly (more quickly than good news). John: Hi, Andy. I'm sorry to hear you got fired. Andy: How did you know about that already? It only happened this morning. John: Bad news travels fast.I called my mother to tell her about my car accident, but my aunt had already told her. Bad news travels fast.