The H5NI highly pathogenic avian influenza virus killed or forced the cull of 400m domestic poultry, infecting more than 63 different countries and causing an estimated $20bn of damage to the global economy. It has infected more than 500 people since it first appeared in 2003, killing 331.
In the past two years, H5N1 has shown up in poultry or wild birds in countries that had been virus-free for several years, with 800 cases in recorded in 2010-11.
The UN’s Food and Agriculture Organisation (FAO) chief veterinary officer Juan Lubroth said that the advance appears to be associated with migratory bird movements, which helps the virus travel over long distances.
He said: “Wild birds may introduce the virus, but people’s actions in poultry production and marketing spread it.”
New incidences have been found in Israel, the Palestinian Territories, Bulgaria, Romania, Nepal and Mongolia. However, it is the new strain emerging in China and Vietnam that is causing the most concern as it appears to be resistant to existing vaccines.
At present it is unknown how the new strain, known as H5N1 - 18.104.22.168, may affect human health.
Vietnam suspended its spring poultry vaccination programme and is reported to be considering a new, targeted vaccination programme.
Lubroth said: “The general departure from the progressive decline in 2004-08 could mean that there will be a flare-up of H5N1 this autumn and winter, with people unexpectedly finding the virus in their back yard.”
“Preparedness and surveillance remain essential. This is no time for complacency. No one can let their guard down with H5N1.”