51 Kids From My Daughter's Middle School Went Home Sick

51 kids from my daughter's middle school went home sick yesterday. My daughter had what others are reporting over the course of four days. Day One - tired, body aches, dry cough; Day Two - tired, body aches, dry cough, complete loss of voice, fever; Day Three - tired, body aches, dry cough, voice coming back, fever, chills, and vomiting; Day Four - slept all day, awoke and felt fine after taking a shower. What would hit so many children so fast? My first response was it had to come from drinking water or something in cafeteria. Not sue if I should be overly concerned or not.