# 3537
Another day, another study.
This time we get a study from the latest issue of the New Zealand Medical Journal where researchers have attempted to calculate the R0 (R-Naught) – or basic reproductive number – of the novel H1N1 virus.
Estimating the reproduction number of the novel influenza A virus (H1N1) in a Southern Hemisphere setting: preliminary estimate in New Zealand
Hiroshi Nishiura, Nick Wilson, Michael G Baker
The R0 is an estimate of how many people an infected host will go on to infect, and is often difficult to estimate with any precision. Early estimates for the novel H1N1 virus gave an R0 of just over 1.1, while later studies moved that up a bit, but still had it a less than seasonal flu.
Today’s study puts the R0 in New Zealand, where it is winter and the virus appears to be transmitting easier, at 1.96 – which is higher than normally seen with seasonal flu.
The authors write:
Given that R is estimated to be 1.96 in a randomly mixing population, this would suggest that 78.6% of the population will experience infection by the end of the pandemic.
Which . . . if accurate, blows the previous estimates of 30% becoming infected out of the water. Even if, as the article below tells us, some of these infections will be sub-clinical.
Of course this is just one study, and it isn’t necessarily the last word on the R0 number, or the attack rate. The virus will have something to say about that, as will our mitigation efforts.
While this study raises concerns, we could very easily see varying R0 numbers and attack rates in different regions of the world.
Critiquing the math and methods of this study are well beyond my pay grade, but hopefully one of the other science bloggers with a background in this sort of thing will weigh in over the next few days.
This report from Radio New Zealand.
Swine flu more infectious than previously thought
Updated at 1:02pm on 24 July 2009
New findings from researchers show the swine flu virus is more easily spread than first thought.
Researchers from the University of Otago in Wellington say this means up to 80% of the entire population of New Zealand could become infected.
Associate Professor Michael Baker says new modelling shows that on average every person who gets the A H1N1 virus in New Zealand is creating two secondary cases.
The findings are published in the latest New Zealand Medical Journal.
Radio New Zealand's health correspondent says it had been assumed up to half of the population could get swine flu.
But Dr Baker says that could reach 80%, with two-thirds showing symptoms.
There are 66 people in hospital with swine flu, 25 of them in intensive care departments.
Meanwhile, the number of deaths from swine flu in New Zealand remains 13.
That's a drop from 14 reported by Chief Coroner Neil MacLean, Thursday.
Judge MacLean says one case has gone from being definitely linked to swine flu to a suspected link.
