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No evidence H7N9 spreads between humans


It’s ten years since SARS (severe acute respiratory syndrome) upset our complacency about infectious diseases and now we are faced by another “new” disease.H7N9 bird flu is currently spreading through China and so far there have been more than 108 cases and the virus has caused at least 22 deaths.

To this point, the outbreak has largely been concentrated in Eastern China. The first case appeared in Shanghai in late February, though the disease was not formally diagnosed until March. Over the past month, the virus has spread into neighbouring provinces as well as to Beijing further north and Henan towards the interior. And in the last few days it has also appeared in Taiwan.

One of the world’s leading flu experts at the World Health Organization (WHO) has labelled H7N9 as one of the most lethal influenza viruses so far encountered. And a number of experts are now claiming the virus may be more transmissible to humans than previous strains of bird flu.

Unlike earlier outbreaks of avian flu, with H7N9 infected birds seem to show no visible signs of illness. Currently the virus also shows no signs of spreading from person to person, but such a transfer cannot yet be ruled out.

Interestingly, the virus seems to replicate the effects of traditional human influenza, largely affecting the elderly. All the deaths so far have involved elderly Chinese, whereas most young children, who have become infected, seem to have recovered without being seriously ill. Many of those infected do not seem to have any contact with infected birds.

As far as infectious diseases are concerned, we inhabit a borderless, interconnected world, where disease agents move almost at will, and where modern modes of transport can move such infections anywhere in the world within a few hours.

Eastern China remains one of the world’s busiest air transport nodes and regular air links to Australia and New Zealand, as well as to many other parts of the world, could easily transport the virus within ten to 12 hours.

Our experience of SARS, avian and swine flu clearly indicate it’s impossible to protect Australia in a time of mass human movement as well as from normal bird migratory patterns.

Airport health inspections and quarantine offer little security insofar as an infected passenger may well show no symptoms of illness at the time of arrival.

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