There have been 4815 confirmed notifications of influenza this year compared to 232 notifications this time last year.

However, Nepean Blue Mountains Local Health District acting director of Public Health Denise Gibbons said there was "no evidence" that the 2019 season was particularly severe.

"The high numbers are due to an unusual summer flu season plus the early start to the winter flu season in May," she said.

The increased instances have been reflected across the Western NSW health region. One person has died from the flu and there have been 1570 confirmed cases in Western NSW.

This represents a 17-fold increase on the 85 cases in the region during the same period last year.

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Ms Gibbons said having a yearly flu vaccination, following good cough etiquette and maintaining hand hygiene were still some of the best ways to stop the spread of flu.

"Free flu vaccines for children aged from six months to under five years of age are being provided under the NSW Government's $2.6 million program," she said.

Western NSW Local Health District communicable disease immunisation manager Sue Turcato said the numbers of influenza numbers did tend to fluctuate from year-to-year and some seasons do have more cases, but there was no way to really predict it.

Peak flu season was usually June to August each year, but Ms Turcato said last year's flu season did not really come to an end.

"Influenza just kept going all through the summer period which means we actually started the flu season earlier this year," she said.

Across NSW there have been 68,909 influenza notifications so far this year with 106 confirmed deaths.

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Statewide there have been more flu cases in young people than any other age group, with 10,943 in children aged 5-9 years old; and 9901 in children aged 0-4 years.

While no vaccines provide 100 per cent coverage, Ms Turcato said if a higher number of people do get a flu shot there is usually less cases of influenza.

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This year free flu vaccines became available for children under five years old and she said this has lead to an increase in people of that age group being vaccinated.

"It's never too late [to be vaccinated] because we've still got two to three weeks of the official flu season, but last year we did see cases go well into the summer months," Ms Turcato said.

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