In general, people will experience gastrointestinal symptoms of nausea, vomiting, abdominal pain and diarrhoea within 12 to 48 hours of infection with norovirus, and may also have systemic symptoms of fever, headache and fatigue. Elderly people and children are prone to dehydration due to repeated vomiting and diarrhoea, mainly manifested as sleepiness, dry mouth, reduced urine output and the desire to cry.