Ten years of fighting bird flu.

In May 1997 a three-year-old boy died of respiratory failure in a Hong Kong hospital. The cause was given as viral pneumonia of unknown etiology, but three months later the infection was identified as H5N1 avian influenza. While the virus had been detected in geese the previous year in Chinas Guangdong province and chickens in Hong Kong in March and May 1997, this was the first evidence that H5N1 had jumped the species barrier to threaten humans. Avian flu went on to kill six people and sicken 18 in Hong Kong until a comprehensive cull of the city's poultry in December that year. Despite the cull, H5N1 started surfacing around the globe, q-he virus has infected wild birds and domestic flocks in at least 55 countries in Asia, the Middle East, Africa and Europe. As of 13 November 2006, there had been 258 confirmed cases of human infection killing 153 people. Ten years later, there is greater awareness and understanding of the threat of a future global influenza pandemic, for which H5N1 is seen as the most likely trigger. A huge interdisciplinary effort is under way to prevent a pandemic and, at the same time, to be prepared for the worst. Despite this, much remains unknown about H5N1. Experts in fields ranging from virology and public health policy to epidemiology, clinical medicine, and the laboratory and veterinary sciences have learned from the milestones of the last decade that will help deal with the threat in the future. The 1997 Hong Kong outbreak was caused by an avian-to-avian reassortment of the virus and, whilst swift and comprehensive culling effectively wiped out that strain, the parent strain continued to reassort and cause subsequent outbreaks in geese and ducks. By the end of 2002 the virus had become lethal to ducks. "By that time we were getting quite concerned, because the virus was making very unusual changes in behaviour and was also affecting wild birds such as egrets," recalled Professor Malik Peiris, a microbiologist at the University of Hong Kong. In early 2003, a mysterious outbreak of atypical pneumonia in Guangdong province was emerging, and by March of that year the outbreak of a new disease, severe acute respiratory syndrome (SARS), had become the focus for academic circles and the media, while having a huge economic impact on travel and other sectors throughout Asia. A cluster of H5N1 cases in a Hong Kong family who had travelled to Chinas Fujian province was another significant development, but concerns about avian flu were largely eclipsed by SARS. With hindsight, the SARS outbreak was in itself an important milestone. Without heightened surveillance in January 2004 in Viet Nam, the avian flu outbreak there might have escaped detection. Similarly, SARS exposed weaknesses in Chinas disease surveillance and response systems. "The ministry of health has taken on board the lessons of SARS," said Dr Julie Hall, WHO's coordinator of epidemic alert and response in China. "It was a pivotal moment in Chinas public health history, as during SARS there was a transparency issue and a huge information vacuum. A lot of that has since been resolved, also in terms of investment in infection control in hospitals. " Since early 2004, H5N1 human outbreaks have been reported in 10 countries and the death toll has risen every year, with South-East Asia suffering the greatest losses of life. Viet Nam and Thailand fared worst in 2004, with 46 cases and 32 deaths between them. By 2005, control measures in Thailand were having an effect, but the disease was emerging in Indonesia, which reported 19 cases and 12 deaths. By 2006, Viet Nam appeared in have reduced the number of human infections to zero, while 55 cases and 44 deaths were reported in Indonesia by mid-November. Progress has been made in Indonesia on the animal health side, although this will remain a five-to-ten-year challenge, said Dr David Nabarro, senior UN system coordinator for avian and human influenza. …