NSW Health is urging members of the public to wash their hands and stay at home if they have gastro symptoms, after a spike in infections brought 1900 people to the state's EDs.

The rise in cases amounts to a 34 per cent jump compared to the same week last year. 

The gastro increase seen at hospitals coincides with a rise in viral gastro caused by norovirus and rotavirus in the community, child care centres and aged care facilities, NSW Health said.

More than 400 of these people had suffered such bad bouts of the infection that they were admitted to hospital, also above the usual range for this time of year. 

It also comes during the worst influenza season in decades, with more than 8000 people with confirmed flu presenting at EDs in the past week alone. 

A total of 32 gastroenteritis outbreaks have been reported in child care centres or aged care facilities in the past week, affecting at least 286 people. 

All of these outbreaks appear to be caused by viral gastroenteritis, four of which were specifically caused by norovirus, NSW Health said.

Viral gastroenteritis is highly infectious and often spread via direct contact with an infected person.

"Norovirus and rotavirus spread easily from person to person, particularly if hands are not carefully washed after using the toilet or before handling food," said Dr Vicky Sheppeard, Director of the Communicable Diseases Branch, NSW Health.

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

"Dehydration often follows bouts of vomiting and diarrhoea, particularly in young children, so people with the virus should rest well and increase the amount of fluids they drink. If people are concerned they should see their local GP," Dr Sheppeard said.

Dr Sheppeard said the best defence was to wash hands thoroughly with soap and running water for at least 10 seconds before handling and eating food, and always wash hands after using the toilet, changing nappies or assisting someone who has diarrhoea or vomiting.

"It is vital that if you or your family contract gastroenteritis that you stay home from work and keep sick children home from school or childcare for at least 24 hours after the last symptom of gastroenteritis."

People who have gastro symptoms should avoid hospitals and aged care facilities to avoid spreading the infection, Dr Sheppeard said. 

"If your work involves handling food, or looking after children, the elderly or patients, do not return to work until 48 hours after symptoms have stopped.

Children are eligible for the rotavirus vaccine at six weeks and four months of age. The vaccine is roughly 70 per cent effective in preventing the infection, and over 85 per cent effective in preventing severe gastroenteritis in infants. 

It is expected to give protection for up to five years.