The stomach virus “going around” is most often norovirus , a very contagious bug that causes sudden vomiting, diarrhea, nausea, and stomach cramps. Recent reports also note a separate rise in cyclospora infections in the U.S., which can cause similar stomach symptoms but is a food- and waterborne parasite rather than a virus.

What people usually mean

Norovirus is the classic “stomach flu” people talk about in outbreaks, especially in colder months and crowded settings like schools, cruises, and nursing homes. It spreads easily through contaminated food, surfaces, close contact, and infected vomit or stool.

Common symptoms

Typical symptoms include:

  • Sudden vomiting.
  • Watery diarrhea.
  • Nausea.
  • Belly pain or cramping.
  • Sometimes fever, body aches, headache, or fatigue.

What to do

Most healthy adults recover in a few days, but dehydration is the main concern, so sip fluids and rest. Wash hands with soap and water, disinfect high-touch surfaces, and avoid preparing food for others while sick and for 48 hours after symptoms stop.

When to get help

Seek medical care sooner if there is severe dehydration, blood in stool, persistent vomiting, confusion, or if the sick person is very young, older, pregnant, or immunocompromised. If symptoms started after eating fresh produce and include severe diarrhea, cyclospora is another possibility.

TL;DR: most likely norovirus, but if there’s strong diarrhea after produce or a longer course, cyclospora is worth considering.