Swine Flu Cases in Australia May Prompt Pandemic Call (Update1) - Bloomberg.com

Swine Flu Cases in Australia May Prompt Pandemic Call (Update1) - Bloomberg.com

June 1 (Bloomberg) -- Swine flu cases in Australia, doubling about every two days, may convince the World Health Organization to declare the first influenza pandemic in 41 years, said Raina MacIntyre, head of public health at the University of New South Wales.

Australia has 401 confirmed cases of the new H1N1 influenza strain, the Department of Health and Ageing in Canberra said in a statement today. The tally, the highest outside North America, has risen from 20 on May 25.

Victoria has 306 cases, up from 173 two days earlier, reflecting the spread of the virus within communities in the southeastern state. Evidence that swine flu has gained a foothold in Australia may compel WHO Director-General Margaret Chan to raise the pandemic alert to the highest of the agency’s six-step system, MacIntyre said in a telephone interview today.

“It must be fairly close to moving into phase 6,” said MacIntyre, who is also professor of infectious diseases epidemiology at the university in Sydney. “It’s clearly spreading in the community in Victoria.”

Disease trackers are looking for evidence of sustained, community transmission of the pig-derived virus outside North America to meet the WHO’s criteria for a pandemic. Such a global epidemic occurs when a new flu strain, to which most people have no immunity, appears and spreads worldwide.

Chan said last month that she will consider factors including how the virus evolves in the Southern Hemisphere during the coming winter before declaring a pandemic.

“WHO is aware of developments around the world and is constantly reviewing the situation,” WHO spokesman Gregory Hartl said in an e-mail today.

Colder Weather

Sixty-two countries have officially reported 17,410 cases of swine flu, including 115 deaths, the Geneva-based WHO said today. Four of every five cases occurred in Mexico and the U.S., where the virus was discovered about seven weeks ago.

The virus has probably infected more Australians than official data show, MacIntyre said.

“Our guess is that for every confirmed case there is somewhere between 2 and 10 unconfirmed cases,” she said, adding that some states were testing more extensively than others.

Mathematical modeling of the epidemic in Australia suggests infections will peak in July and that swine flu will be the most common circulating influenza strain in the country this winter, she said. Australia’s winter runs from June 1 to Aug. 31.

Flu particles persist longer in the air during colder, drier weather. The bug is also transmitted more easily in winter because people tend to huddle together indoors.

“It would make sense that the next country for it to take off in would be somewhere that’s going into winter rather than in the Northern Hemisphere where they are going into warmer weather and you’d expect things to quiet down,” MacIntyre said.