Hong Kong H5N1 Alert Raises Vaccine Concerns
Recombinomics Commentary 13:15
December 9, 2008

Hong Kong last had an outbreak on a farm in February 2003, showing the Government's prevention measures have generally been working well. However, Dr Chow said he is very concerned about the factors leading to this new outbreak as the first chickens to die were those which had not been vaccinated. The incident is being investigated.

The above comments from the Hong Kong alert raise concerns over the vaccine status of the H5 fatal infections of 60 chickens on a Hong Kong (Yuen Long district) farm (see updated map).  Hong Kong had a major outbreak in 1997, which lead to human fatalities, and after a series of poultry outbreaks, instituted strict controls.  Consequently, there have been no reported H5N1 outbreaks on farms in Hong Kong since 2003.

However, H5N1 in wild birds in Hong Kong has been reported at this time of the year for the past several years, raising concerns of a significant H5N1 reservoir, which has been kept off Hong Kong farms due to protective measures, which includes vaccination.

Consequently, the death of 60 chickens has led to the culling of over 80,000 and has raised vaccine concerns.  There have been outbreaks in adjacent Guangdong Province, and concerns about failed vaccinations were also raised.

The earlier outbreaks in wild birds involved the Fujian strain (clade 2.3), which included clade 2.3.4 and 2.3.4/2.3.2 reassortants.  Clade 2.3.2/2.3.4 reassortants were also identified last spring in northern Japan, Southeast Russia, and South Korea.  The South Korean outbreak was the largest reported to date and included a symptomatic soldier/culler who was H5 PCR confirmed.  Similarly, earlier Guangdong outbreaks were also linked to human cases in Shenzhen in 2006 or a case in 2008.

Thus, the latest outbreak in Hong Kong, which is almost certainly H5N1, raises additional vaccine issues and human infections in the area.  Similarly, these outbreaks in the Hong Kong regions also raise concerns about the lack of reports of H5N1 infections in China.

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