Early assumptions that swine flu would be benign because of reports of low death rates in Canada and the United States may have made people nonchalant about its seriousness, says a Massey scientist.
As at July 10, New Zealand had reported six deaths from swine flu and 1272 confirmed cases. The total number of cases in the community would be considerably higher however, says Professor Mick Roberts, a mathematical biologist at the University’s Institute of Information and Mathematical Sciences at Albany.
Professor Roberts has been researching the spread and virulence of the (A) H1N1 virus, or swine flu, in recent months and says conflicting reports in April about the severity of the virus resulted because of the time delay between the onset of infection and death.
Professor Roberts has just returned from a three-month research stint at Utrecht University in the Netherlands working on a Marsden-funded project with Professor Hans Heesterbeek to develop mathematical models that will help with understanding the evolution and transmission of viruses.
They were focusing on HIV/AIDs and seasonal flu when the swine flu broke out in Mexico. The pair interrupted their research to analyse data on infection and death rates in Mexico, Canada and the United States, in order to assess its virulence.
A paper Professor Roberts co-wrote with Dutch epidemiologists was presented last week to a meeting of the World Health Organisation’s Network for Pandemic Human Influenza. It looked at the case fatality ratio of swine flu – the ratio of deaths from an infectious disease to the number of cases. “We examined data at the beginning of the pandemic for the United States and Canada in April and May, and compared it with data on the number of confirmed cases and deaths in Mexico. The death rate was similar in all three countries,” he says.
However some media reports stated that more than 150 people had died of swine flu in Mexico by the end of April, despite the World Health Organisation issuing a statement saying nine had died. Cases from the same period resulted in two and four reported deaths in the United States and Canada respectively. There are now 25 reported deaths and 7983 confirmed cases of swine flu in Canada, he says.
Professor Roberts says people should not underestimate the seriousness of swine or seasonal flu. Last year 472 people were hospitalised in New Zealand for seasonal flu, and every year about 400 die from flu-related conditions. “A lot of people lump colds and flu together. A cold is a very different virus to the flu,” he says. ”Seasonal flu can be a serious illness.”
Professor Roberts has previously worked with the WHO Pandemic Influenza Research Group, to establish how a new virus could spread through New Zealand. He believes New Zealand health authorities are correctly managing swine flu, which the World Health Organisation last month declared a worldwide pandemic.
hat-tip Sally
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