Secretary for Health, Welfare & Food Dr York Chow says registering all food importers will help trace sources and distribution, and ensure safety.

He told reporters today that registering importers will help ensure food items that claim to meet safety standards and have health certificates be better monitored.

On avian flu, Dr Chow said there will be increased risks of transmission to humans in winter as the virus will be among some wild and migratory birds.

"The most important aspect is to ensure it is not going to be developing into a pandemic or a new virus. The important issue is to identify the cases, to isolate them, to trace the source of infection of these people and the poultry infection so it will not spread further.

"This is the real risk that the whole world is facing. As long as we can be vigilant in our surveillance and identification of suspected cases, we will be able to control this to a limited extent."

Dr Chow said there is little evidence that chilled or frozen poultry can transmit the virus into an avian flu infection in humans. Noting all live poultry have been vaccinated, he said the antibody level of chickens crossing the boundary and from local farms will be checked daily to control any suspected avian flu outbreak.