Swine flu more contagious than thought
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The swine flu virus is more contagious than previously thought and is spreading faster than the 1918 Spanish flu, according to new research published today.
The letter written by University of Otago, Wellington researchers and published in the New Zealand Medical Journal today said that every person who caught swine flu would pass it on to an average of about two other people, meaning up to 79 percent of the population could be affected.
Associate Professor Michael Baker and Dr Nick Wilson from the Department of Public Health worked with Holland-based mathematical modeller Dr Hiroshi Nishiura to give the first published estimate for the reproduction of the virus in the Southern Hemisphere.
The number of people each person who catches swine flu will subsequently infect is known as the reproductive number.96, which is somewhat higher than the number we have previously used in modelling estimates,” Mr Baker said.
“Our best estimate of the reproduction number for the Influenza A virus in New Zealand is 1.5 which was published early in the pandemic based on data from Mexico.
“To date we have tended to use a lower estimate of 1. While up to 79 percent of the population could catch swine flu over the course of the epidemic, many would not realise they had it, they said in the letter.”
The researchers calculated this by analysing the spread of the virus from 2 June, when the first case of community transmission was recorded, to 16 June, before health authorities stopped recording all cases due to the rapid growth.
Mr Baker said the higher prevalence in New Zealand could be to do with do with the virus hitting the Southern Hemisphere in winter and due to large clusters of infected people in other cases.
While up to 79 percent of the population could catch swine flu over the course of the epidemic though many would not realise they had it, they said in the letter.6 percent.
Previous reports published in Japan suggested the reproduction rate there could be as high as two to 2.
However, the projected rate here could be reviewed after a more accurate analysis of the demographic and if the public responded to measures to help restrict the spread of the virus, Dr Baker said.
However, the rate here could be lower if the public responded to measures to help restrict the spread of the virus, Dr Baker said. .
The researchers pointed out that although it was more contagious than Spanish flu which killed thousands, the mortality rate was still very low – an earlier study released by the pair said the number of deaths could be as low as one in 10,000 cases.