There were 2244 flu cases confirmed in NSW in the four weeks to March 3, almost double the 1144 official cases in February last year, according to NSW Health's latest Influenza Surveillance Report.

In the week ending March 3, there were 12 reported cases of flu in the Murrumbidgee Local Health District.

Across NSW, there were eight flu outbreaks at aged care facilities during February.

NSW Health's communicable diseases branch director, Vicky Sheppeard, said several factors were contributing to the high level of unseasonal flu cases.

"Some of the increase follows a late influenza season across tropical parts of Australia, which affected northern NSW, and now it's likely that travellers returning from the northern hemisphere are bringing flu home with them," Dr Sheppeard said.

"Unusually high levels of influenza activity are being seen in most states and territories, with the national reporting rate more than three times the average for this time of year."

Dr Sheppeard said while it was unlikely the high number of cases will lead to widespread infection in the community, it was concerning to see outbreaks at aged care facilities.

"Residents of aged care facilities will have little immunity left from last year's flu vaccine, so it's important to not expose them to the risk of influenza," Dr Sheppeard said.

"If you have a fever, cough or runny nose please postpone visiting elderly relatives until you recover."

Free flu vaccines for high-risk people for the 2019 season will be available across Australia from mid-April.