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Keeping an eye on avian flu

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THE emergence of a new strain of avian influenza virus in China has reignited public interest in the disease while again raising concerns about the potential for a human pandemic. The new virus, influenza A(H7N9) seems to be unusual in that, although some H7 viruses (H7N2, H7N3 and H7N7) have occasionally been reported to infect humans, no human infections with the H7N9 subtype have been reported previously. Also, unlike other avian influenza strains, including highly pathogenic avian influenza H5N1, which causes large-scale die offs in poultry flocks, it is hard to detect in poultry because it causes few signs of disease in birds.

The World Health Organization (WHO) reported three cases of human infection with the virus on April 1. By April 9, 24 cases had been confirmed by laboratory testing; seven of those people had died. Of the remaining cases, 14 were considered serious and three mild. All of the cases had been reported in China, where no human infections with H7 viruses had been reported previously. The WHO said that the Chinese government was investigating the outbreak and more than 600 contacts were being monitored.

Although the virus had infected people, there was, the WHO reported on April 9, no evidence of ongoing human to human transmission. However, it pointed out, any animal influenza virus that develops the ability to infect people might theoretically cause a human pandemic, and investigations, involving human and animal health authorities, were continuing to determine if there was a significant risk of community spread.

Although the source of infection and mode of transmission were uncertain, it advised that it would be prudent for those who might be exposed to the virus to follow basic hand, respiratory and food hygiene measures, including cooking food thoroughly.1 Meanwhile, with the virus being hard to detect in animals, the Food and Agriculture Organization (FAO) advised that strong biosecurity and hygiene measures were needed to reduce the risk of virus transmission.2 Preventing disease outbreaks depends on effective surveillance, and the FAO and the WHO commended China on reporting cases quickly and making information about the virus available to the public.

Research remains vital in the fight against diseases like avian influenza. However, the emergence of H7N9 has added fuel to the controversy that continues to surround some of the research being undertaken in this field. In 2011, when research teams in the USA and the Netherlands announced that they had worked out how to produce a form of H5N1 avian influenza virus that could spread between people, the US National Science Advisory Board for Biosecurity (NSABB) sought to stop publication of their findings, mainly because of concerns that they might be useful to bioterrorists. After much debate, the work was subsequently published, although the episode led to wider debate among scientists about the wisdom of conducting research that could lead to the production of viruses that might be more virulent than those found in nature. During 2012, researchers engaged in such research suspended their studies so the issues could be debated but, in January this year, the controversy was reignited when they announced that they were lifting the moratorium.

The scientists involved argue that they have a public responsibility to undertake such work because of the risk that an H5N1 virus capable of being transmitted between mammals may emerge naturally, and that it is important to be prepared for this. However, other scientists argue that the risks of such research outweigh the potential benefits. In a strongly worded editorial in Nature last month, Simon Wain-Hobson, of the Washington-based Foundation for Vaccine Research, argued that this kind of work should be suspended so that the global ramifications could be more thoroughly discussed and explored. He also argued that an independent risk-benefit assessment was needed.3 Meanwhile, Ab Osterhaus, of the Erasmus Medical Centre in the Netherlands, which is engaged in such work, was reported by Reuters last week as saying that the emergence of H7N9, and the need to know how likely it might be to spread between people, demonstrated precisely why this kind of research was necessary.4

One can see where scientists on both sides of the debate are coming from, but it would clearly be in everyone's interest for some sort of consensus to be reached on how best to proceed. In the meantime, avian influenza remains a prime example of the need for a ‘one health’ approach to emerging diseases, and of the need to strengthen veterinary surveillance and develop new tools for tackling the challenges they present at source.

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