ESR said the picture was much the same for the rest of the country.
But its strategic health intelligence manager, Dr Lisa Oakley, said things could change quite quickly.
"Generally it's this time of year that we start to see flu cases peak. Although the numbers that we are seeing are still low compared to previous years, our surveillance is telling us that they may start to rise soon," Oakley said.
"It's still not too late to get your flu vaccine this year. It's the best protection for you and your family against the flu."
The vaccine for the flu has been updated to counter several strains of influenza found overseas.
The Whanganui DHB said the vaccine was available and would be until the end of the year.