Our city's elaborate defences against bird flu have, once again, been breached. This time, dead chickens at a farm in Yuen Long have been confirmed to be infected by the H5 virus. The government must move swiftly to discover the source of the infection and review the system. It is clearly not working as well as it should do.
Most worrying is the discovery that chickens which had been vaccinated against the potentially deadly virus are among those infected. This would seem to confirm warnings sounded earlier in the year that the effectiveness of the vaccine, such an important component in our defences, is fading. Steps must be taken to ensure that, as far as possible, vaccines provide adequate protection.
There is a disturbing sense of deja vu about the return of the bird flu virus. It was only in June that poultry at four wet markets were found to be infected, leading to the culling of thousands of birds. The latest outbreak is a reminder that we remain vulnerable, despite all the efforts that have been made to guard against the virus.
About 80,000 chickens at the affected farm and 10,000 more it had sent to a wholesale market will have been culled by today. The import and export of live chickens will be banned for three weeks. Retail and wholesale markets have been shut as workers start disinfecting facilities. These are necessary measures, but not long-term solutions.
It is too early to determine the extent of the outbreak. Inspectors are collecting and testing samples from other farms and markets. Hopefully, the latest incident is confined to the single farm known to be affected so far. Its owner is to be commended for speedily reporting the incident to the authorities. But, if it had involved a less responsible owner, detection would have taken much longer, and the virus would have had more time to spread.
The infection of vaccinated birds raises fresh concerns. Scientists who monitor the vaccination programme have been warning about its declining effectiveness. The government introduced vaccination at all local farms in 2003. University of Hong Kong microbiologists say we are not far from the day when the vaccines will become useless. Worse, they warn that some vaccinated chickens may not show symptoms and so spread the virus as 'silent carriers'. Hong Kong has been using the same vaccine for years. It is time to consider whether a change would improve prevention.
