Number crunchers put their spin on flu toll

More than 3000 people could die from a mild influenza pandemic, according to Treasury figures.

The agency's April 29 briefing paper to Finance Minister Bill English on the potential economic impact of a swine flu pandemic includes assumptions for a "severe scenario", based on the 1918 flu pandemic, and a "mild scenario" based on the 1957 and 1968 pandemics.

The current pandemic of swine flu is regarded as moderate so far in New Zealand - the virus is highly infectious and spreads easily in the community, but for most people it causes only mild to moderate symptoms, although these can still be unpleasant.

The Treasury says that although much is uncertain about how swine influenza may evolve, based on the mild scenario possibly 30 per cent could become infected, of whom 0.25 per cent could die.

That suggests more than 1.2 million people could be infected, of whom 3200 could die.

However, the Ministry of Health's latest estimates - contained in a document circulated to the health sector on Friday by Steve Brazier of the National Health Co-ordination Centre - are that half the population could catch the pandemic virus and that the number of deaths is not likely to exceed 200 and may be substantially lower.

The deputy director of public health, Dr Fran McGrath, said yesterday that the ministry did not have firm assumptions about infection and case-fatality rates because the situation was evolving.

"The current estimate from the World Health Organisation is that about 2 per cent of cases will develop severe illness."

Seasonal flu affected about 10 per cent of people each year and caused around 400 deaths, Dr McGrath said.

The confirmed swine flu cases, past and current, stood at 386 yesterday, although the actual number will be far higher.