Norovirus causes a relatively short, intense illness characterized by nausea, vomiting, diarrhea, and abdominal cramping.
The most common symptoms are sudden onset of vomiting and watery diarrhea, although stomach cramps and pain also often occur. Some people experience fever and body aches. Symptoms usually start 12 to 48 hours after being exposed and typically last about 1 to 3 days.
Although symptoms usually only last 1 to 2 days in healthy individuals, norovirus infection can become quite serious in children, the elderly, and immune-compromised individuals. In some cases, severe dehydration, malnutrition, and even death can result from norovirus infection, especially among children, and among older and immune-compromised adults in hospitals and nursing homes.
In England and Wales, 20% of those over the age of 65 die due to infectious intestinal illness other than Clostridium difficile. Recently, there have been reports of some long-term effects associated with norovirus, including necrotizing enterocolitis, chronic diarrhea, and post-infectious irritable bowel syndrome, but more data is needed to support these claims.