Pandemic 'already started' say Australian experts
Two experts on infectious disease in Australia say a flu pandemic has effectively already started because of the widespread number of cases there.
Robert Booy, professor of Child Health at the University of Sydney in New South Wales, urged the World Health Organisation to take action regarding a shift from the current alert phase 5 to the top level, phase 6: "The WHO can't keep scratching their heads, they have to make a decision," he said.
Professor Booy, who works at the Children's Hospital, Westmead, said the H1N1 virus was "unstoppable" and would continue to spread around the world. He expressed surprise that the WHO had not already declared a pandemic - a global epidemic of a new flu strain - because the H1N1 virus "fulfilled the criteria of community spread".
As yesterday's post made clear, the WHO has said once we have "community level outbreaks" in another region outside the Americas, then a pandemic will be declared. This means that the virus must be spreading widely, beyond schools and unrelated to travel.
Professor Booy said his neighbouring state of Victoria now had so many cases they would no longer be testing people with flu symptoms in the community, but rather limiting the test to those who needed hospital treatment. "We have community transmission in Victoria," he said.
Victoria has by far the bulk of Australia's swine flu cases. The Australian government said that of the country's 1,211 total confirmed cases, 1,011 had been reported in Victoria.
The number of cases in Australia have risen four-fold in a week. Professor Booy said this was unsurprising. "The cycle of infection is about two days. For every one person with the virus, another 1.5 people get infected, so that gets you to a four-fold rise in six to seven days".
Professor Booy said thankfully the virus was causing mostly mild symptoms. "We have had some hospitalisations, and one person in intensive care, but all are doing well," he said. Fewer than 10 of the flu cases nationwide have required hospital admission. There have been no deaths.
Raina MacIntyre, professor of Infectious Diseases Epidemiology at the University of New South Wales, said according to the WHO's definition of a pandemic, "we are in Phase 6; technically we are there already."
But she added, "it's just a guideline, and when the definitions were devised they didn't factor in severity. I think the WHO approach is reasonable given that there would be widespread economic, tourism and trade implications if a pandemic was declared".
Professor MacIntyre explained that the traditional thinking was that a pandemic would be caused by a new haemagglutinin antigen. This is one of the surface proteins on the flu virus, and is responsible for it binding to infected cells.
"We thought it would be caused by an H5 or an H9 type, rather than H1 which is not really new. When you look at the immunological response of the various age groups, people over 65 have a good level of protection, and only people under 18 have no immunity while many young adults have little immunity."
Professor Booy, who helped draw up Australia's pandemic flu plan said "We had many assumptions and one was that a new flu virus would cause high mortality caused by something really novel. The H1 gene has been with us for centuries."
But he warned that the virus could mutate or "drift" in the coming months. "We already know of cases where people have got double infections - both H1N1 and seasonal flu - and that's what you need for viruses to reassort."