Caliciviruses cause infection in people of all ages. This family of viruses is divided into four types, the noroviruses (see Norovirus) being the most common. It is now thought that at least 50 percent of all foodborne outbreaks of gastroenteritis can be attributed to noroviruses. Norwalk virus is a type of norovirus. People infected with one of these "stomach viruses" may develop vomiting and diarrhea, fatigue, headache, and sometimes muscle aches. Norovirus symptoms appear within 1 to 3 days of exposure.
Adenovirus infections occur mainly in children under 2 years of age. Of the 49 types of adenoviruses, one strain affects the gastrointestinal tract, causing vomiting and diarrhea. Symptoms from this "stomach virus" typically appear 1 week after exposure. Adenovirus infections occur year-round.
Astrovirus infects primarily infants, young children, and the elderly. This type of "stomach virus" is most active during the winter months. Vomiting and diarrhea appear within 1 to 3 days of exposure.