Flu cases are spiking in NSW with several outbreaks in schools as winter approaches and COVID-19 lingers.

NSW Chief Health Officer Kerry Chant said cases are rising quickly throughout the community, with outbreaks detected in boarding schools.

The state had 2000 new flu cases notified in the week to Saturday, while emergency departments saw about 60 presentations for flu-like illness that required hospital admission over the same period, Dr Chant said.

The 2000 weekly cases come after 1025 in the prior seven-day period.

Health authorities are also seeing a rise in the proportion of people testing positive for influenza, with 9.1 per cent in the week to Saturday compared with 5.3 per cent in the previous week.

Boarders who caught the flu at four schools where outbreaks have been reported have been told by health authorities to isolate.

Dr Chant stressed that getting a flu vaccination shot was important for the community at large.

Those considered at higher risk of severe illness from the flu include Aboriginal and Torres Strait Islander children, pregnant women and people aged over 65.

Others at risk include people with serious health conditions such as severe asthma, diabetes, cancer, immune disorders, obesity and kidney, heart, lung or liver disease.