The possibility of a major resurgence of Highly Pathogenic Avian Influenza H5N1 - also known as bird flu - has prompted the United Nation's FAO (Food and Agriculture Organization) to advise health authorities around the world to step up surveillance and readiness. There are signs that a mutant strain of Bird Flu is making inroads in Asia and other parts of the world. The FAO describes current the risks to human health as "unpredictable".
Out of 565 individuals who have been officially infected with the H5N1 virus since 2003, at least 331 died, says the World Health Organization (WHO). Cambodia has had 8 deaths so far this year, one in August 2011; every infected person died.
Over 400 million domestic poultry have had to be destroyed since 2003 because of H5N1. Experts say the economic damage exceeded $20 billion worldwide, before bird flu was supposedly eradicated from the majority of the 63 nations infected in 2006 (bird flu peak).
Even so, H5N1 continued to be endemic in six countries - Viet Nam, Indonesia, India, Egypt, China and Bangladesh.
The number of domestic and wild birds infected fell from 4000 in 2006 to 302 in 2008. However, over the last twenty-four months, numbers have been steadily rising. 800 cases were reported in 2010-2011.
H5N1 spreading in both poultry and wild birdsH5N1 has been spreading in both domestic poultry and wild bird populations since 2008, the FAO reports. The spread seems to be linked to the movement of migratory birds, says Juan Lubroth, Chief Veterinary Officer of FAO.
Lubroth explained that over the last two years H5N1 infections have been reported in poultry and wild birds in countries that have not seen an infection for many years.
"Wild birds may introduce the virus, but peoples' actions in poultry production and marketing spread it."
Mongolia, Romania, Nepal, Bulgaria, Palestinian Territories and Israel have had reports of poultry and wild birds infected with H5N1.
A mutant virus strain which is resistant to existing vaccines is appearing in China and Viet Nam, Lubroth added.
Viet Nam suspended its vaccination campaign this spring. H5N1 is endemic in northern and central parts of Viet Nam - it is in these parts of the country that a new strain has been spreading. The new strain is known as H5N1 - 188.8.131.52.
Viet Nam on high alertViet Nam authorities say their veterinary services are on high alert and may initiate a new, targeted vaccination campaign later on this year.
Malaysia, Thailand and Cambodia may be threatened by this circulating virus - there is a possibility that Korea and Japan could eventually become affected too.
"The general departure from the progressive decline observed in 2004-2008 could mean that there will be a flareup of H5N1 this fall and winter, with people unexpectedly finding the virus in their backyard."
Viet Nam, Indonesia, India, Egypt, China and Bangladesh, where H5N1 is firmly established, face the biggest problems. However, Lubroth warns that no country is safe.
"Preparedness and surveillance remain essential. This is no time for complacency. No one can let their guard down with H5N1."
Written by Christian Nordqvist