Outbreaks of the virus occur seasonally with rotavirus and norovirus commonly circulating in the community.

A second peak of the virus usually starts at the beginning of each year coinciding with the intake of new ­children to early childhood centres.

“Although the cause of most outbreaks in institutions is not diagnosed, all outbreaks occurring in institutions in the past month appear to have been cause by viruses that spread easily from person to person,” Hunter New England public health physician David Durrheim said.

“Symptoms can include nausea, vomiting, diarrhoea, fever, abdominal pain, headache, and muscle aches and usually last between one and two days, sometimes longer.

“Illness can worsen quickly in ­children and the elderly, so if people are concerned they should see their local GP.”

More than 60 institutional outbreaks (including childcare centres, nursing homes and hospitals) were reported last month, affecting at least 803 people.

“The best defence is to wash your hands thoroughly with soap and ­running water for at least 10 seconds before handling and eating food, and always wash your hands after using the toilet or changing nappies,” Dr Durrheim said.

“We advice staying home from work and keeping children home from school or childcare when sick.”