Ducks carrying tiny satellite transmitters on their backs are being tracked in Mai Po wetlands by scientists trying to determine their migratory routes and their connection to deadly bird flu viruses. Meanwhile, tempers are flaring over government-imposed restrictions on the import of live chickens. Last Saturday, a chicken trader dived into Victoria Harbour in protest and, earlier this week, a band of poultry sellers tried to break a police cordon at the Murray Building in Central. They are furious that only 7,000 mainland chickens a day are being allowed in during the Lunar New Year instead of the usual 20,000. The spectre of bird flu is with us again, as it has been periodically since the H5N1 - or bird flu - virus killed six of the 18 people who contracted it here in 1997 and led to an unprecedented mass culling of some 1.4 million birds and the closure of the trade for two months. Scientists said that stopped the virus from turning into the sort of pandemic not seen since we gave Hong Kong flu to the world in 1968. But despite four outbreaks in the 11 years since the first, and a global re-emergence of the deadly virus since 2003, the early fears have given way to complacency because a flu pandemic has failed to materialise. The poultry trade is angry at having to carry the can for a public health scare when they believe H5N1 bird flu was long considered a 'chicken plague', affecting only poultry. There is particular fury this winter that the supply of fresh chickens from the mainland is being kept at a normal-day level for the Lunar New Year, the most important festival on the Chinese calendar and the time they would normally expect to make a killing. But health chief York Chow Yat-ngok said the city could not risk a flu outbreak, not this winter when the threat regionally is 'reasonably high'. Hong Kong has cause for alarm, having been at the 'serious response level' since December 9 when H5N1 killed chickens at a Yuen Long farm. The farm will remain closed until March. The debate will continue as Hong Kong enters the peak flu season, which is three weeks away, according to the Centre for Health Protection. Yet a confluence of events in recent weeks is cause for concern: an outbreak of H5N1 in a Hong Kong farm last month, just six months after the virus reappeared in four wet markets; a two-month-old baby stricken with a milder strain, H9N2; and the stirrings of a seasonal flu that could be more severe than last winter when four children died and scores were taken ill, prompting the closure of preschools and primary schools ahead of the Easter holidays. Also, the mainland has reported this month that three people have died of H5N1 flu - a 16-year-old from Guizhou province , a 27-year-old woman from Shandong province and a 19-year-old woman in Beijing. A two-year-old baby, meanwhile, is in hospital in Shanxi province . Her mother died on Saturday in Hunan province but no samples were taken from her, the Ministry of Health said. Meanwhile, 377,000 chickens were culled in Jiangsu last week after bird flu was found in two areas. The ministry said there was no evidence of a large-scale outbreak as the cases were scattered across different provinces and were 'isolated, unrelated and did not show significant mutations of the H5N1 virus'. The first alert on the outbreaks in Jiangsu came from the Programme for Monitoring Emerging Diseases (ProMed), a cascading e-mail system run by the International Society for Infectious Diseases. Vincent Martin, senior technical adviser on avian influenza at the Food and Agriculture Organisation's (FAO) mainland office, said: 'We did not receive any new report of a poultry outbreak. What was unusual this year was the outbreak in domestic poultry in Jiangsu province and human cases in provinces which had never experienced the disease before. 'The Hunan and Guizhou cases are more in line with what we observed last year, that is to say cases in areas where we know the disease has been present in the past or the virus is still circulating in poultry.' The World Health Organisation's China office said its experts were looking at vaccine failure for the 'hidden outbreaks' in poultry that could have infected humans. But Dr Martin said the Ministry of Agriculture had informed him that its vaccination results were 'excellent'. 'I know they have developed good and effective vaccines but the task is huge and almost overwhelming,' he said. About 5 billion birds need to be vaccinated on the mainland, a difficult task with so many backyard poultry operations. In Hong Kong, such operations are banned but smuggled chickens from the mainland remain a problem. 'It is always possible that some poultry in less biosecure production systems are not vaccinated correctly,' Dr Martin said. 'However, only a thorough investigation will be able to give the right answers.' He said such investigations would have to explore the possibility of vaccine failure and of H5N1 mutation. Dr Martin said the FAO still recommended vaccinating chickens 'if it is not the only measure implemented and if it is done in a proper way. 'We issued some guidelines about vaccination and we know it can work, but it must be accompanied with other measures such as biosecurity, surveillance, early reporting and communication, among others,' he said. Wild birds have also been a target for blame in the spread of the H5N1 virus, which jumped the species barrier for the first time in 1997 and has spread east to Europe and Africa since 2003, killing 249 people worldwide. In a satellite-tracking project launched on December 10, scientists from the FAO, WWF Hong Kong, the University of Hong Kong's department of microbiology and other international scientific bodies are investigating if wild ducks, which winter in Mai Po and surrounding areas, are spreading the virus. Malik Peiris, HKU's world-renowned bird flu expert and a team member, said satellite tracking of migratory birds would help settle the question, in concert with other research. So far, HKU has tested more than 30,000 samples of healthy ducks and found them all negative for H5N1. The risk of a wild bird directly infecting humans is 'negligible', said Professor Peiris. He said mainland cases of hidden infections, where the birds did not show symptoms, mirrored those in Egypt and Indonesia and always occurred when there was 'increased activity in the poultry flocks during winter'. 'I would strongly suspect there are poultry infections that are responsible for human cases. I don't think those human cases are coming from wild birds,' Professor Peiris said. The reasons for this included backyard flocks where surveillance may not be good. 'And if you have vaccinations, that may mask the disease. Especially in ducks, you can have infections without having obvious disease. All these are real problems.' His advice for travellers for the Lunar New Year is to avoid places where there have been cases in poultry or humans and stay away from live poultry. As to bird flu fatigue, Professor Peiris said the public and media went from one extreme to the other, 'either becoming hyperanxious, imagining that the flu is coming tomorrow. Then, if that does not happen, the response is they go to the [other] extreme and feel there is no threat at all.' He said the virus is entrenched in more places than it was three or four years ago, including Africa. Hong Kong, at the tip of what has been called the flu epicentre, is the microcosm of that global complacency. Just six years ago, Hong Kong was the epicentre of the global outbreak of the severe acute respiratory syndrome virus caused by a nasty mutant of the coronavirus which, until then, had just caused common colds. It was established that the coronavirus had somehow mutated in civet cats sold and eaten in wet markets in Guangdong. The Yuen Long farm outbreak was a wake-up call for experts. Results of epidemiological and vaccine studies, which are being awaited, will provide UN agencies, the FAO and the World Organisation for Animal Health with guidance on what more can be done to prevent people dying from bird flu and stem a possible pandemic. The 'comprehensive epidemiological report' to fully understand what caused the outbreak in the 20-year-old farm is yet to be submitted to the Food and Health Bureau. Other farm owners first blamed smuggled eggs - the farm is also a hatchery - before the owner claimed it was sparrows. Ornithologists have debunked that claim. A hint of what's to come could be gleaned from Dr Chow's recent remarks. 'If you remember, during the past few years, we always increase the number of imported chickens from the mainland during the festive seasons like Chinese New Year,' he said. 'Also, the last few times when we discovered the H5 virus in the chicken droppings as well as in the chicken farm in Hong Kong, are related to the time we increased the import during the festive seasons. So, we feel this time we have to limit the number of chickens to the existing level.' Whether the government will stand firm and put public health before poultry profits remains to be seen.