Press Releases

The Investigation Group on Epidemiological Study appointed by the Secretary for Food and Health today (March 5) released its report on the investigation into the highly pathogenic avian influenza H5N1 outbreak in a chicken farm in Ha Tsuen, Yuen Long, in December 2008.

The investigation group examined the details of the outbreak, revisited the regulatory regime of poultry farms, analysed the virus recovered from the index farm and test samples taken from other local farms, and recommended improvement in biosecurity measures for the index farm and other local farms.

Outlining the report findings on the avian influenza outbreak at a press conference today, the convenor of the investigation group, Dr Thomas Sit, said, "The investigation group noted that the outbreak was confined to the index farm in Ha Tsuen. The outbreak was detected early to enable immediate action to be taken to prevent further spread of the disease. There was no indication of spread of infection to other farms."

Genetic analyses showed that the virus belongs to the family Clade 2.3.4, a clade which is commonly found in the south China region. The virus was most closely related to and shared a common ancestry with isolates detected in poultry retail markets in Hong Kong in June 2008 and a dead wild bird found in Tsing Yi in March 2008. No mutation associated with virulence in mammals was found.

"As with many epidemiological studies of this nature, it is difficult to determine the exact cause of the outbreak. The investigation group considered that the H5N1 virus was most likely to have been introduced to the farm by wild birds. Droppings of wild birds could have contaminated the dust and dirt near the entrance of one of the two affected sheds which was subsequently blown into the shed area during windy days. Once the virus had gained entry, farm workers could have contributed to its spread to the other shed via contaminated hands/gloves and/or clothing," Dr Sit explained.

Also speaking at the press conference, the Director of Agriculture, Fisheries and Conservation, Miss Cheung Siu-hing, noted that the investigation had revealed some biosecurity vulnerabilities and breaches on the index farm, including wild bird protection, and possible non-compliance by workers with biosecurity measures (including hand/glove hygiene) relating to entry into the chicken sheds.

The investigation group recommended the following measures for improving the biosecurity on the index farm:

* modify the structure of one of the affected sheds so that the shed area is fully covered by its roof and add a solid partition on the side facing north to protect against wind gusts;
* cover all open soak away pits and wells to avoid gathering of aquatic birds on the farm; and
* improve bird protection facilities.

The investigation group also put forward improvements to biosecurity measures for all poultry farms to strengthen the procedures for prevention of avian influenza infection, which include:

* further tightening of biosecurity through tailor-made biosecurity plans, record keeping in standard templates, provision of hand washing facilities and refresher courses;
* facilitating early detection by increasing the inspection frequency and sampling size of blood tests for vaccinated chickens; and
* preventing spread of avian influenza through scattered distribution of sentinels and segregating the operations relating to the rearing of breeder and broiler flocks.

"The Agriculture, Fisheries and Conservation Department (AFCD) has taken on board the recommendations and will facilitate the implementation of enhanced biosecurity on local farms. Discussions and planning with individual farmers are already underway.

"Biosecurity measures on the farms are one of the most important preventive measures against the threat of avian influenza virus. We call on the farmers to stay vigilant and comply with the biosecurity requirements at all times. The AFCD will continue to work with them and provide the necessary support," Miss Cheung said.

The investigation group's convenor was the Assistant Director of Agriculture, Fisheries and Conservation (Inspection & Quarantine), Dr Thomas Sit. Members of the group included the Head of the Department of Microbiology of the University of Hong Kong, Professor Yuen Kwok-yung; Head of the Laboratory Animal Unit of the University of Hong Kong, Dr Lo King-shun; and representatives of the AFCD, Department of Health and Food and Environmental Hygiene Department.

The full report has been uploaded onto the AFCD's website, www.afcd.gov.hk, for public viewing.

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