Almost 2200 confirmed cases of the flu have been reported over the summer in NSW - double the number seen last year.

An "unusually high" number of people have been hit with the flu this summer in NSW - double that seen in 2018.

NSW Health on Friday said there had been 2196 confirmed cases of influenza across the state in the five weeks to February 3.

While it's not unusual for a spike in flu cases at this time of year, as people return from holidays in the colder northern hemisphere, the national reporting rate is almost three times the average, the department said.

"In NSW, our rate has doubled from notifications in January last year but thankfully once home in summer temperatures, influenza doesn't tend to spread as easily from person to person," Dr Vicky Sheppeard said in a statement.

The department has recommended pregnant women, who are due to give birth before April, get a free flu shot from their GP or pharmacist.

"For the rest of us, it is best to wait until the 2019 flu vaccine becomes available in April or May," Dr Sheppeard said.