The parasite doesn't exist, but scientists in Europe and the US are working on developing a vaccine for an influenza virus they fear could one day spark the world's biggest pandemic, scientists here said.

This virus, commonly known as bird flu, which is one of the most rapidly transmitted virus, has given rise to a series of epidemics in east and southeast Asian countries such as China, Vietnam and Thailand, killing a large number of people.

The infection is currently spread by the consumption of infected fowl. But the minute it mutates itself to spread human-to-human, it could affect neighbouring countries in South Asia, the most populated region in the world.

"The virus transmits itself much more rapidly than most diseases we know today. In addition, it picks up and changes its surface identity, so that every two years we have a new strain of flu virus," Barry Bloom, a member of the advisory committee of the World Health Organisation (WHO), told in an interview.

Bloom had come to India to attend the 92nd Indian Science Congress in Ahmedabad, India's most prestigious event for scientists. He then left for New Delhi to meet doctors and scientists there.

According to Bloom, who is the dean of Harvard School of Public Health, US, the WHO has already collected flu virus strains of the past few years and using them it has predicted the possible strains for the next 15 years.

Under the WHO banner, over 87 labs across the US and Europe are now engaged in formulating a new vaccine for a flu virus that could transmit itself from person-to-person, Bloom said, adding that the most devastating global pandemic that occurred in 1918 had taken a toll of up to 40 million people because the flu virus then had been of a very different strain from what had been seen till then.

"A vaccine might be ready by the end of next year, but the question then is who will take it on from there? As many as 10 million people will have to be infected, but who will distribute the vaccines before the virus strikes? And by the time the virus strikes, it might just be too late," Bloom said.