The Food and Agriculture Organisation (FAO) has warned that the deadly bird flu, which first appeared in 2003, is rearing its head again in Asia and other countries.
The organisation has said that there are signs of a mutant strain of H5NI spreading and urged heightened readiness and surveillance against a possible resurgence of the highly pathogenic avian influenza.
The H5NI virus infected 565 people since its first outbreak in 2003 and killed 331 of them, according to the estimates of World Health Organisation (WHO).
Further, it killed or forced the culling of more than 400 million domestic poultry and caused around $20 billion of economic damages across the globe. It was consequently eliminated from most of the 63 countries that bore the brunt of it.
Remains endemic
However, the FAO report says that H5NI still remains endemic in Bangladesh, China, Egypt, India, Indonesia and Vietnam, although the number of outbreaks in domestic poultry and wild bird populations came down steadily from an annual peak of 4,000 to just 302 in mid-2008.
These countries are likely to face the biggest problems even as no country can consider itself.
The outbreaks in the six countries have risen progressively since 2008 with nearly 800 cases reported in 2010-11. At the same time, a renewed geographic expansion of the virus has been noticed both in poultry and wild birds and this seems to be associated with migratory bird movements.
Migrations
According to Mr Juan Lubroth, Chief Veterinary Officer of FAO, the migrations help the virus travel over long distances and H5NI has started showing up in poultry and wild birds in countries that were free from the virus for several years.
The recently affected areas are in Israel and the Palestinian territories, Bulgaria, Romania, Nepal and Mongolia.
A further cause of concern is the appearance in China and Vietnam of a variant virus, which is apparently able to sidestep the defences provided by the existing vaccines, says the FAO report quoting Mr Lubroth.