Cruise ships like to say their problems are from Norovirus however, some incidences have been proven to come from shellfish taken from too warm waters. This is when only some aboard ship get ill. Noro is very contagious so 2 people in same cabin should get it but if only one does you can be sure one ate shellfish.

Since the post says Sonesta has problems in March or April repeatedly, maybe it's more of a seafood poisoning? Once stayed at Divi (in March) ate mussels there and got just as sick as a friend who described their noro symptoms. Hubby did not get sick the entire trip. Needless to say I no longer eat shellfish NOR do I eat at Divi!!