Health chief York Chow Yat-ngok has raised the specter of "a silent infection among poultry" in the wake of a suspected human bird-flu case just across the Hong Kong border.Chow's fears were raised by a report that a truck driver surnamed Jiang, 31, was suspected of having contracted the deadly H5N1 virus in Shenzhen.
Xinhua News Agency said Jiang developed a fever, back pains and cough on June 3 and was admitted to hospital Friday.
He is said to be in critical condition but four other members of his family did not have similar symptoms.
They were still placed under observation.
Chow, the secretary for health, welfare and food, said Wednesday Jiang had no specific contact with poultry though he had eaten chicken bought by his wife from a market in the Longgang district.
"His risk was not much higher than that of any citizen in Shenzhen," he said.
"We feel that there might be a possibility of a silent infection among some of the poultry, particularly backyard- farm poultry.
"They might be carrying the virus without exhibiting symptoms. That is what we are concerned about."
A Shenzhen official said three initial tests on Jiang by a local laboratory were positive for the H5N1 bird flu strain. Confirmatory tests by a Beijing laboratory are pending.
The World Health Organization said the case is likely to be confirmed.
Hong Kong authorities are screening travelers arriving from Shenzhen by land for fever, and will step up health inspections of poultry im
ported from the mainland. Chow said if his fears are correct, it could pose big problems.
"If humans get into contact with these [silent carriers] they may get infected without us knowing exactly the source of infection," Chow said.
Experts say the use of bad or substandard vaccines may prevent birds from dying or even falling sick, but may not stop them from getting infected and shedding the virus in their stool.
This problem has also been observed in Indonesia where the H5N1 virus has killed at least 37 people.
Feng Shaomin, spokesman of the Health Ministry in Guangdong, said authorities have stepped up inspection of chickens from the mainland.
In Hong Kong, the Hospital Authority has enhanced its surveillance program under which all public hospitals are required to report all patients suffering from pneumonia.
Meanwhile, a six-member Hong Kong team comprising doctors, veterinarians and food-safety officials visited Shenzhen Wednesday and met with authorities to study the latest case.
Speaking after the meeting, a Department of Health spokesman said since the patient was in a critical condition, he was unable to provide details that would help uncover the path of transmission.
In Beijing, a health official attempted to calm public fears.
"It is an individual case and there is no sign of a concentrated outbreak in any province," said Ministry of Health spokesman Mao Qunan, stressing "the public need not panic."
Beijing WHO spokesman Roy Wadia said the organization received notification of the Shenzhen case Tuesday - about the same time the mainland government informed the Hong Kong authorities and other relevant parties.
He said China had not requested any assistance from WHO at this moment.
"China has had a fair amount of experience with human H5N1 cases so far. If confirmed, as is likely, this case will be the 19th such case reported in the mainland," he said.
"It has been difficult in China and other countries for agricultural/animal health authorities to spot outbreaks in poultry, especially small outbreaks or sporadic poultry H5N1 cases, and this continues to pose a serious challenge to efforts to fight bird flu.
"Normally, cases in animals should alert public health authorities to the presence of H5N1 in the environment, but in China [and many other countries] almost all the human cases have been identified first before animal outbreaks in the area have been detected."
Waida added: "So animal surveillance remains key to the effort to fighting avian influenza. Unless the animal surveillance system is significantly strengthened, China will continue to face a huge challenge in tackling bird flu."
The H5N1 virus first surfaced in Hong Kong in 1997, killing six of the 18 people infected, prompting the culling of more than two million fowl.
A mass cull of chickens alleviated the problem locally, but the H5N1 virus continued to circulate among birds in Asia, most recently among migratory species that carry the virus for long distances.
Scientists are worried the virus may mutate into a strain that is easily transmissible among humans, triggering a pandemic.
