Adele Wong
Monday, February 02, 2009
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"Are there poultry out there that are carriers of the disease but do not show symptoms? This point is cause for concern since, if this is correct, it will be the most difficult issue for us to handle," Chow said.
"We are now seeing people suffering from bird flu being linked to contact with birds who are sick even though there has been no outbreak.
"We are concerned about whether there have been some small changes in the way poultry reacts to the flu virus."
Chow aired his fears at a Heung Yee Kuk function after the mainland confirmed another case of human bird flu infection.
There have been eight human cases of H5N1 infection in the mainland since December, five of whom have died.
The most recent case involves a 21-year-old woman in Hunan who was taken sick on January 23. The woman, who has a history of exposure to sick poultry, is in stable condition, according to the mainland's health ministry.
Hong Kong University microbiologist Ho Pak-leung warned: "The virus is at our front door - very likely in Guangdong [at this moment]. Something unusual is happening."
But he said there is no evidence to suggest birds can carry the H5N1 virus without showing symptoms of the disease, and that the chances of "silent" carriers are minimal.
"If we look at the eight human cases of bird flu in the mainland, the majority were the result of exposure to sick or dying birds," he said. "There was contact, and it wasn't simply exposure to live animals that displayed no symptoms.
"We have not found evidence as yet that animals can survive [bird flu] without showing symptoms."
Nevertheless, he said the eight cases are of concern "as this has been the highest occurrence within a narrow timeframe since the first mainland case was documented in 2003."
Regarding the lack of an outbreak among poultry before human infection, Ho said a likely explanation is that most animals have already been immunized, but that vaccines are not always 100 percent effective.
He believes measures should be stepped up to prevent cross-border
infection and poultry smuggling by boat, especially with many travelers returning from the mainland after the Lunar New Year holiday.
"Prevention is more important than surveillance," he said.
He also encouraged the government to speed up vaccination research with the mainland.
Health chief Chow also made reference to the discovery last Thursday of two geese and one duck found dead on Sha Lo Wan beach on Lantau.
All were confirmed to have been infected with H5N1.
He said investigations are centered on whether the birds had been dumped there by individuals who owned poultry or whether they had died in the mainland and been washed ashore.
Chow also requested mainland officials to investigate whether there have been any bird flu outbreaks along the Pearl River Delta.
There are no poultry farms or live poultry within a three-kilometer radius of Sha Lo Wan.
Islands district councillor Chau Chuen-heung said that, within the vicinity of Sha Lo Wan, it is unlikely that villagers are keeping backyard poultry - a once common practice that has since been banned.
"One would be able to hear noises such as rooster calls if anyone kept poultry, but you don't hear that anymore here," she said.
hat-tip Muscade
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