The researchers say that further work will be needed to produce more robust estimates for New Zealand and this latest estimate could be reduced after more accurate demographic analysis, and if public hygiene behaviour and health interventions are effective.

Dr. Wilson says the results reinforce the need for those with influenza symptoms to do everything they can to prevent infecting others - by staying away from work and school while ill and practicing good 'cough etiquette' - all of which will help to lower the spread of the new virus.

The team say though the current estimated reproduction number is higher than that of the Spanish influenza pandemic of 1918-19, the mortality rate in this pandemic is very low compared to that disaster, in which thousands died.

Earlier this month in a separate published study, the two New Zealand scientists estimated that the mortality rates in developed countries from this pandemic could be as low as one death out of 10,000 cases for this new pandemic strain.

The research is published in the New Zealand Medical Journal.