But Norovirus is very contagious.
CDC does not track it in the USA, but in the UK and EU the norovirus tally often reaches many thousands.
In PA two years ago there was a Boy Scout camp in which almost all the campers got noro over a two week period.
If it lasts a day or two it’s not influenza. One or two days and it could be gastroenteritis or noro or Norwalk virus.
But that still would not be food poisoning caused by leaving food unrefrigerated, as the other poster implied. It could indicate inadequately washed produce, but that is not at all what was stated.