The H5N1 bird flu virus is widely regarded as a possible trigger for the world's next influenza pandemic because of its high mortality rate in humans and its rapid spread among birds across the globe in recent years.

But not enough is being done - from disease surveillance to vaccine manufacturing and mundane logistical details - according to experts at a Singapore conference on avian flu and other infectious diseases.

There has got to be an increase in vaccine manufacturing facilities, said Peter Palese, a microbiology professor at the Mount Sinai School of Medicine in New York. "In a pandemic, there would be a lot of difficulty in securing vaccines from producers," he said.

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The global flu vaccine production capacity is only 350 million doses per year - a fraction compared to a world population of more than six billion.

The shortfall becomes even more stark with a few drugmakers now promoting multiple doses for each person for better protection.

The H5N1 virus remains largely a bird disease and is hard for humans to catch. But it has killed 154 people since late 2003 and there are now several strains of the virus in circulation.

It is considered a novel virus against which people have no natural immunity, which partly explains its unusually high mortality rate of 60 percent. This also underscores the threat to humanity should the virus evolve into a form that easily spreads from person to person.

Drugmakers told the conference they are trying to get around simple, but daunting logistical problems in developing H5N1 vaccines for humans.

"Syringes and needles will be in short supply in the event of a pandemic," said James Young, president of research and development at MedImmune, which markets a nasal spray vaccine that fights the common flu.

"We are looking at changeable tips - after spraying into the nose of one person, you can change the tip and go to the next person," he said.

The conference also heard repeated calls for wider and tighter surveillance of the H5N1 virus in birds.

Nearly all human victims of H5N1 caught the virus from sick or dead chickens and one obvious way to prevent a pandemic would be to wipe out the disease in birds. But such intervention is easier said than done.

In countries such as Indonesia and China, where rural households typically keep small numbers of chickens, the spread of the disease has often gone unreported, hampering efforts to stamp out the virus.

"There needs to be a greater amount of surveillance data collected and shared," said Frederick Hayden, a University of Virginia virologist now working on global flu planning for the World Health Organisation. REUTERS