At the moment, experts say, there has not been enough evidence of mild avian-influenza infection to drastically reduce the disease's mortality rate, nor even to revise it. But, they concur, the possibility merits further study.

Reduced virulence is a possible indicator that avian influenza is preparing itself to become more transmissible -- as this column has noted for the past 11 months, reduced virulence can lead to increased transmissibility, as diseases are less able to infect large swaths of people when they kill their host before the infection has been passed on -- and it is this fact that health officials wish to monitor more closely, especially as the rainy season in Southeast Asia and the autumnal bird migrations are likely to lead to increased reports of both avian and human infections.

Speaking over the weekend and cited by Canada's CBCNews, Dr. Michael Osterholm, avian-influenza expert and director of the University of Minnesota's Center for Infectious Diseases Research and Policy, said: "We need to keep monitoring it.

"Because, frankly, one of the indications that there may be a changing epidemiology with this is, in fact, if we start seeing larger and larger percentages of individuals who are asymptomatic or only mildly ill that we can clearly confirm as having H5N1 infection."

The Indonesian case, which was made public last week, involved a man who had blood tests for H5N1 performed. Although the man was not ill, the test results showed he had been infected with avian influenza, most likely earlier this year, when he cared for his sister, a confirmed bird-flu case.

While looking after his sister, the man had complained of abdominal pain and had suffered from a persistent cough, but his symptoms were so mild that he was not tested for signs of H5N1 infection.

In South Korea five workers who had culled infected poultry between 2003 and 2004 -- out of more than 2,000 who were submitted to blood tests -- were found to have H5N1 antibodies in their blood, a sure sign that they had been infected with the disease at some stage, although none displayed avian-flu symptoms at the time.

While these cases were no doubt lucky to have survived avian flu, and to have suffered from it so mildly, they may in turn be the key to finding a cure for the disease that -- using current rates of infection and mortality -- has killed nearly 60 percent of known cases.

What remains now is for more work to be done into investigating why these lucky few were not only capable of fighting the disease, but did so without even knowing they were infected.

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The World Health Organization and Indonesia are at odds over what constitutes a human case of avian influenza. The disagreement follows an earlier redefining of human avian-influenza infection in humans by the WHO, which saw the number of confirmed Indonesian cases rise.

The Indonesian Health Ministry has so far abstained from adopting the new definition of bird-flu infection. This refusal will not change the global infection statistics, however, as the official figures are those released by the WHO.

Santoso Soeroso, head of the Health Ministry's avian-influenza verification team, explained that the WHO's definition has been altered so that it is less restrictive, meaning that cases of bird-flu infection can, in theory, be identified and treated earlier.

According to the new WHO standards, those suffering from acute lower respiratory infections -- difficulty breathing, shortness of breath, fever and cough -- should be treated as possible cases of avian influenza.

The Indonesian Health Ministry currently uses acute higher respiratory infection as a sign of possible bird flu.

Soeroso said: "It's like catching fish with big-holed nets. We may be able to identify possible cases when patients reach the stage that the flu is incurable."

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According to a report in the Financial Times over the weekend, the current Thai political crisis that has resulted in the government being deposed in a bloodless military coup may have contributed to the spread of avian influenza in the country.

Thailand had been working hard to combat the spread of avian influenza in the country's poultry, and until earlier this year it appeared that their efforts had been effective. But an outbreak in poultry along the Mekong River on the Laotian border earlier this summer showed that the virus was still present in a country believed to have defeated it.

Dr. David Nabarro, the United Nations' senior coordinator for avian influenza, told the Financial Times that he thought the changing political face of Thailand -- whose parliament was dissolved earlier this year by former Prime Minister Thaksin Shinawatra, who was ousted this week in a bloodless coup -- may have contributed to the disease's re-emergence.

"You don't maintain control over this disease unless there is regular top-level direction from a committed senior political figure that wants to be sure that the necessary activities are being undertaken," Nabarro said.

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