Public health officials in Yala’s Muang and Betong districts untangle wild birds from trap nets yesterday so they can be checked later for avian flu.

The bird-flu virus H5N1 has become more complex, probably as a result of the antiviral drug oseltamivir, and that has caused complications in detecting it in the laboratory, the Public Health Ministry said yesterday.

Dr Paijit Warachit, director-general of the Department of Medical Sciences, said there had been laboratory failures in detecting the lethal virus during the first tests of the two most recent cases of bird flu this year.

"It's been more difficult to test [the virus] this year," he said. Both cases were confirmed as H5N1 in a subsequent test.

"It may be because the progress of the disease [in humans] has become more complicated," Paijit said.

One factor could be the effect of oseltamivir, or tamiflu, which is believed to be the only effective defence against bird flu in humans.

The drug, Paijit said, was only able to prevent the virus from replicating and did not destroy it. That meant little of the virus was excreted into that part of the respiratory tract where specimens are taken for testing.

"[Medical staff] took swabs in that area, yet as it turned out there was not enough of the virus to enable them to detect it," he said. "The virus was deeper in the respiratory passage."

It had also just been learnt that with these two cases it was found the bird-flu virus had been buried even further into the respiratory tract than the influenza virus, Paijit said. In order to get a complete specimen for testing, health workers were told to probe deeper with their equipment.

Since 2004 when bird flu emerged in Thailand, the ministry has tested more than 4,000 people for the virus and the failure rate due to incomplete specimens had been only 3 per cent, he said.

But that figure had risen to 20 per cent this year, Paijit said.

"We need to continue our studies to see whether the virus will become more and more difficult [to detect] in the future," he said.

In response to findings by Chulalongkorn University scientists that a new form of the virus had been detected in Nakhon Phanom, Paijit said the strain had yet to infect humans.

The virus was found in poultry and it would probably be more virulent than the old one, he said.

Meanwhile, caretaker Public Health Minister Pinij Charusombat yesterday called a meeting with about 500 private hospitals and clinics to seek their cooperation on bird-flu surveillance and reporting of patients suspected of having bird flu.

"It's a concern that some private hospitals may be failing to report a suspected case for fear it could scare their patients," Pinij said. Any health facility that failed to report a case would face harsh punishment.

The Public Health Ministry had also joined with the Bangkok Metropolitan Administration and the Drug Stores Club of Thailand in stepping up screening of patients with suspected bird-flu symptoms.

Bangkok Governor Apirak Kosayodhin said he had ordered poultry checks to be increased and had set a limit on the movement of poultry into Bangkok in order to prevent avian flu being spread in the capital.

Arthit Khwankhom

The Nation