Twenty deaths this year have been swine flu-related but health authorities say the total number of flu-like infections has been lower than previous years - and has fallen well below average levels.

Auckland District Health Board yesterday confirmed the death of a 37-year-old man at Auckland City Hospital earlier this month, bringing its tally of H1N1 strain-related deaths to seven. The latest victim had no underlying medical conditions.

The death of an 82-year-old Auckland man earlier this month has also been confirmed as H1N1-related. An underlying health condition may have contributed.

The World Health Organisation confirmed last year that healthy young people were an at-risk group for severe H1N1 influenza. As with seasonal flu, those with underlying chronic conditions such as diabetes, cancer or heart disease were also at risk.

Fifty Nelson school children contracted the H1N1 flu in July and more than 400 Wairarapa children were ill by the following month.

The World Health Organisation's Global Influenza Programme head Sylvie Briand said healthy young people typically arrived very late to healthcare facilities, meaning treatment came late in the course of the disease. This could explain the severity.

H1N1, or "swine flu", is so called because the virus can infect both pigs and humans, though pig to human infection is rare.

The virus first appeared in Mexico in March last year. By the end of April, there were 1614 cases, with 103 deaths and around 400 patients hospitalised.

New Zealand's first cases came the following month. Ten Rangitoto College students showed symptoms after returning from a three-week language trip to Mexico. Their symptoms were relatively mild and all recovered.

At the pandemic's height in July, up to 20 per cent of intensive care unit beds were occupied by H1N1 patients. Deputy Director of Health Dr Darren Hunt says New Zealand H1N1 infection numbers continue to drop. There were 724 admissions of confirmed H1N1 cases this year, down 35 per cent from last year's 1122.

WHO declared the pandemic officially over in August.