The 7 million+ residents of Hong Kong consume more poultry than can be produced locally, so every week a large quantity of live poultry is imported from neighboring Guangdong Province. In order to protect both the residents, and the poultry operations, in Hong Kong a small number of chickens in each batch is tested – both by PCR and by Serology – for avian flu viruses.
While PCR testing can tell if there is a current infection, serology can show evidence of earlier infections. And that can help define just how big a problem a virus is becoming.
Testing is particularly important for H7N9, as the virus does not cause symptoms in poultry, but can be deadly for humans. Often we only first learn of an outbreak in poultry when exposed humans fall ill.
Last year the use of both testing methods by Hong Kong led to considerable political friction, as powerful mainland agricultural interests felt the serological tests were unfairly prejudicial against their product (see Hong Kong: Dr. Ko Wing-man On H7N9 Testing Of Poultry).
Today we learn that a small number of imported chickens have tested positive by serology (but not PCR) for the H7 virus, and that additional PCR testing is underway to determine if there are any actively infected birds in this shipment. Results should be available in a few hours.
The Government today (December 30) found in a consignment of imported live chickens a number of samples tested positive in H7 avian influenza (AI) serological tests, whilst all swab samples collected from the same consignment of live chickens were tested negative in H7 Polymerase Chain Reaction (PCR) tests. According to the established risk management protocol, the relevant government departments are now collecting 120 additional swab samples from the same consignment of live chickens to conduct PCR testing. Preliminary results will be available around midnight at the earliest.
The serological test serves as a surveillance measure on birds or farms to determine if they have been infected with H7 AI in the past. While a positive result in serological test reflects the fact that the live poultry have been infected in the past, it does not mean the concerned chickens are carrying AI virus at the time when being tested. To ascertain if individual birds are carrying AI virus, the accepted protocol is to rely mainly on PCR testing for H7 AI which is currently in use.
If the additional 120 swab samples are all tested negative in the H7 PCR tests, it reflects that the consignment of live chickens is not carrying AI virus and can be released to the market. For good measure, the Hong Kong Government will notify the relevant Mainland authorities for strengthened surveillance and investigation on the registered farm concerned. After both sides have agreed on the investigation result, the farm in question may continue to supply live poultry to Hong Kong.
If any of the additional 120 swab samples is tested positive in the H7 PCR tests, it would suggest that the consignment of live chickens carries H7 AI virus. The Government will accordingly activate the AI contingency plan.
Ends/Tuesday, December 30, 2014
Issued at HKT 20:55