norovirus

According to the CDC, an outbreak of the Norovirus is defined as:

An outbreak of norovirus is defined as an occurrence of two or more similar illnesses resulting from a common exposure that is either suspected or laboratory-confirmed to be caused by norovirus.

So when more than half of those attending a party gets stricken with similar stomach issues, that should be cause to report a possible Norovirus incident. For Hawaii, the Disease Investigative Branch can be contacted at (808) 586-8362.