Blood-serum tests aimed at boosting Hong Kong's defences against the deadly H7N9 bird flu virus have so far returned no positive results, authorities on both sides of the border say.
The tests, showing whether chickens have been exposed to the H7 virus of which H7N9 is a strain, indicate whether the farms the birds come from are or have been infected.
In Hong Kong, the Agriculture, Fisheries and Conservation Department said 90 samples taken from a group of 12,000 chickens raised at three farms in the New Territories all tested negative.
Samples are being taken both from chickens raised on local farms and the 7,000 chickens imported on a daily basis. None of the local birds have tested positive, and last night the Food and Environmental Hygiene Department said all 120 samples taken from imported birds at the border had tested negative.
Across the border, a first batch of 56 samples taken on Wednesday had also tested negative, said Lo Wei, deputy chief of the Shenzhen Inspection and Quarantine Bureau's animal quarantine division.
"Our agreement with Hong Kong includes running [serum] tests on live poultry supplied to Hong Kong," Lo said. "Should there be positive test results, we would immediately halt supply to Hong Kong."
Samples were tested as soon as they arrived in his laboratory and results were available within 24 hours, he said.
Secretary for Food and Health Dr Ko Wing-man said that if any chicken tested positive all birds would be culled and the wholesale market would be closed for 21 days for disinfection.
The new test replaces a gene test for live poultry introduced in April last year after the virus began to spread on the mainland.
A gene test can show only whether a chicken is carrying the virus. The serum test can show whether even those chickens not carrying the virus have been exposed to it. Such chickens may have avoided infection after developing antibodies.