Advisory Council on Food and Environmental Hygiene
Reducing the Risk posed by Quail
in the Development of H5N1 Viruses
This paper provides information on the basis for the administration's proposal to separate the sale and transport of live quail from other live birds and invites Members' views on the proposal.
2. The 1997 H5N1 avian influenza virus isolated in Hong Kong was unique in being able to cause serious disease in both man and poultry. This particular strain of H5N1 virus was eliminated from poultry in Hong Kong in late 1997 and has not returned.
3. Genetic analysis of this virus has provided very strong evidence to suggest it was derived from a recombination of another H5N1 influenza virus, first detected in geese in southern China in 1996, and two other influenza viruses. These other two strains of virus, a quail-type H9N2 influenza virus and an H6N1 virus, are still present in quail in the region.
4. The control measures we introduced in 1998 were aimed at keeping H5 influenza viruses out of Hong Kong's retail markets. These measures were not directed at H9 and H6 influenza viruses, which occur widely in poultry in the region but do not cause significant disease. Consequently there is a possibility that birds entering our markets can have these viruses. In fact, subsequent surveillance testing of birds at markets, at the border and in farms has shown that quail are frequently infected with quail-type H9N2 and H6N1 influenza viruses.
5. The presence of these quail-type viruses alone in the markets does not represent a major threat to public health. Although two cases of infection in infants with quail-type H9N2 viruses occurred in Hong Kong in 1999, the disease these viruses caused was relatively mild and self-limiting. Nevertheless, allowing these viruses to co-exist with H5 influenza viruses provides an opportunity for reassortment and formation of an H5N1 virus that could have characteristics similar to the 1997 strain.
6. In May 2001, we had incursions of an H5N1 goose-like reassortant virus into retail markets where quail H9N2 and H6N1 viruses were also present. From the genetic analyses performed so far there is no evidence to suggest that reassortment with viruses carried by quail occurred.
7. Although we have enhanced our control measures for H5 avian influenza viruses there is a possibility that incursions with an H5 virus can occur again. Hence, we wish to minimize the risk of this virus developing into a strain capable of causing serious disease in man through reassortment of its genes with those of other influenza viruses.
8. We can reduce the risk posed by quail-type H9N2 and H6N1 viruses by preventing live quail from being kept with other poultry in farms, live bird markets and during transportation.
9. It has been suggested that these measures should also be extended to types of poultry other than quail, such as guinea fowl, pheasant and chukar. At present, we do not have sufficient information on the nature and prevalence of quail-type viruses in these other species to justify such a move. We will continue to work with experts in the field to ascertain whether these birds pose a genuine risk if they are allowed to be sold in poultry stalls with chickens.
10. We propose to amend existing legislation to require segregation of quails from other birds during production, transportation and sale. Members are invited to endorse this proposal.
Agriculture, Fisheries and Conservation Department
Environment and Food Bureau