The number of Aussies with flu has surged in NSW, with cases up 35 per cent according to the latest NSW Health figures.
Under 16's are most badly affected, weekly figures from the end of June show, but all ages are suffering with the infection.
"Numbers of people with fever and cough symptoms have been increasing since February," NSW said.
Cases of Whooping Cough are also on the up, especially in children aged five to 14.
Plus there have been "unseasonably high presentations to emergency departments" for pneumonia and children and young adults.
Health bosses said they did not know the cause.
In May they also flagged a rise in flu cases.
The state's health authority urged everyone to get vaccinated for flu - especially those at a greater risk of severe disease.
The latest COVID-19 strain spreading across the world
"Influenza is more serious than the common cold," NSW Health director of health protection Dr Jeremy McAnulty said.
"It can cause pneumonia, make chronic underlying medical conditions like diabetes, lung and heart disease much worse requiring hospital admission and causing death.
"Complications can occur in anyone but are most likely in those at higher risk of severe illness."
Meanwhile cases of COVID-19 and RSV are down.
RSV cases are highest in children under five, but are "decreasing or stabilising," NSW Health said.
Meanwhile cases of COVID-19, which are down two per cent, are mostly of strains related to the JN1 variant
