A pregnant woman and three children are among 27 people hospitalised with serious complications caused by influenza in the Nelson-Marlborough region.
The Nelson Marlborough District Health Board told 1 NEWS 16 people have been admitted to Nelson Hospital since April, and 11 people at Wairau Hospital in Blenheim.
The Board urged people who haven't already, to get their flu vaccination.
Last year the flu season was late and light. As it started late the days were already getting longer, air temperatures rising and people being less confined. The flu season petered out but lingered over summer to a minor extent.
But, this year the flu is peaking early with all those severity lessening seasonal effects moving in the wrong direction - meaning that it is only going to get colder and wetter.
The Board also said there is concern following the situation in Australia, with more than 10,000 people diagnosed with flu in March, compared to 3173 in March last year.