Despite a fall in reported cases, NSW Health is urging people yet to have a flu shot this year to consider having one now.
Children under five years old are among those specifically encouraged to get vaccinated.
Young children are particularly vulnerable to complications from influenza.
NSW Health's director of communicable disease, Vicky Sheppeard, said even though we are nearing the end of winter when the risk is greatest, people can catch flu any time of the year.
The latest Influenza Surveillance Report shows 4424 flu cases for the week ending August 4, down from 6126 notifications in the previous seven days.
This takes the NSW yearly total to 69,055.
There have been 21 additional deaths of people aged over 25 years reported, bringing the annual total to 127 confirmed influenza deaths.
"The flu can affect people of all age groups, even those who are fit and healthy," Dr Sheppeard said.
"Vaccination is your best protection against the bug and it's still not too late to get the jab."
She said that there are plentiful supplies of influenza vaccine and urged parents of children under five years of age, those over 65 years and others vulnerable to the flu to visit their GP as soon as possible.
"Just like the common cold the best precautions people can take against the flu are to ensure they wash their hands thoroughly, cover their coughs and sneezes and stay home if they are unwell," Dr Sheppeard said.
People who are sick are encouraged to stay away from small children and elderly relatives or friends until they have recovered.