Manila, Nov 24 (DPA) The World Health Organisation (WHO) warned Tuesday of a possible resurgence of bird flu amid new cases of the disease in poultry in Egypt, Indonesia, Thailand and Vietnam.

The Manila-based WHO Western Pacific Office said the presence of the H5N1 virus in poultry placed those in direct contact with the birds at risk of getting infected with the disease.

It added that it was also closely monitoring the risk of the H5N1 virus combining with the H1N1 swine-flu virus to produce a new and deadlier strain.

'We don't know if this is possible, but we are certainly aware of the risk,' said Shin Young-Soo, WHO regional director for the Western Pacific. 'We are on alert for this development.'

The WHO noted that the H1N1 virus that killed more than 6,000 people around the world since April was a new strain that resulted from 'reassortment' or combination of the avian, swine and human strains of flu in pigs in Mexico.

Urging countries to remain on alert against bird flu, Shin stressed that influenza viruses were unpredictable.

'In areas where the H1N1 is endemic, we and our partners and national governments are working to build surveillance systems to identify changes in the behaviour of the virus,' he said.

'We are also focusing on early-response capacity to reduce the potential threats to human health,' Shin added.

Since 2003, outbreaks of H5N1 have been reported in poultry flocks in 60 countries in Asia, Europe and North Africa, leading to the culling of millions of birds.