A dramatic surge in flu cases amid the COVID-19 pandemic is putting NSW hospitals under "significant pressure" as staff fall victim to the viruses.
After two years with very few cases, Health Minister Brad Hazzard says a "horror flu season" has "hit NSW earlier and harder than it has for many years".
About 2000 workers are absent from hospitals on an average day.
"It is absolutely crucial that you go and get your flu vaccine as soon as possible," he said.
There have been 14,812 reported flu cases and 3349 people have arrived at emergency departments with influenza-like illnesses in NSW this year.
More than 8000 cases of COVID were reported on Tuesday, with 1234 people in hospital with the virus, 38 of them in ICU.
Health Secretary Susan Pearce said the double whammy of a resurgence of flu in the midst of the unrelenting COVID-19 pandemic was putting emergency departments "under significant pressure".
"Please do not call triple zero or attend emergency departments for non-urgent issues," she said.
"We are urging the community to support us during this challenging period by making sure those who need emergency medical care can receive it by saving ambulances and emergency departments for saving lives," she said.
Anyone unsure whether they should go to hospital should visit healthdirect.gov.au or call Healthdirect on 1800 022 222.
Chief pediatrician Matt O'Meara said children aged six months to five years were particularly vulnerable to flu, with at least 10 per cent of youngsters admitted to hospital with the virus so sick they needed intensive care.
"Parents can reduce the risk of that happening just by getting their child vaccinated," he said.
Thousands of children under 10 were coming to hospital, with some being admitted, while thousands of teenagers have also been affected.
Chief Health Officer Dr Kerry Chant urged people to continue taking simple precautions to protect themselves from viruses.
"This includes wearing a mask indoors when you can't physically distance, staying at home when you're unwell, and remembering to practise good hand hygiene," Dr Chant said.
NSW Ambulance Commissioner Dr Dominic Morgan said paramedics were also under extraordinary pressure.
Before COVID-19, ambulances would respond to about a million calls a year. Last year 1.43 million triple-zero calls were answered.
