MANILA, Philippines - The Food and Agriculture Organization (FAO) is urging heightened readiness and surveillance against a possible major resurgence of the H5N1 Highly Pathogenic Avian Influenza amid signs that a mutant strain of the deadly bird flu virus is spreading in Asia and beyond, with unpredictable risks to human health.
The H5N1 virus has infected 565 people since it first appeared in 2003, killing 331 of them, according to World Health Organization (WHO) figures.
The latest death occurred earlier this month in Cambodia, which has registered eight cases of human infection this year, all of them fatal.
The Philippines, along with Brunei, continues to remain free of the bird flu virus.
Since 2003, H5N1 has killed or forced the culling of more than 400 million domestic poultry and caused an estimated $20 billion in economic damage across the globe before it was eliminated from most of the 63 countries infected at its peak in 2006.
However, the virus remained endemic in six nations, although the number of outbreaks in domestic poultry and wild bird populations shrank steadily from an annual peak of 4,000 to just 302 in mid-2008.
But outbreaks have risen progressively since, with almost 800 cases recorded in 2010-2011.
According to the FAO, 2008 marked the beginning of renewed geographic expansion of the H5N1 virus both in poultry and wild birds.
The advance appears to be associated with migratory bird movements, according to FAO chief veterinary officer Juan Lubroth.
He said migrations help the virus travel over long distances, so that H5N1 has in the past 24 months shown up in poultry or wild birds in countries that had been virus-free for several years.
“Wild birds may introduce the virus, but peoples’ actions in poultry production and marketing spread it,” Lubroth noted.
Recently affected areas are Israel and the Palestinian territories, Bulgaria, Romania, Nepal and Mongolia.
A further cause for concern, Lubroth said, is the appearance in China and Vietnam of a variant virus apparently able to sidestep the defenses provided by existing vaccines.
Most of the northern and central parts of Vietnam,
which suspended its springtime poultry vaccination campaign this year, have been invaded by the new virus strain, known as H5N1-2.3.2.1.
The H5N1 is also endemic in these areas.
Vietnam’s veterinary services are on high alert and reportedly considering a novel, targeted vaccination campaign this fall.
Virus circulation in Vietnam poses a direct threat to Cambodia, Thailand and Malaysia as well as endangers the Korean peninsula and Japan.
Wild bird migration can also spread the virus to other continents.
“The general departure from the progressive decline observed in 2004 to 2008 could mean that there will be a flare up of H5N1 this fall and winter, with people unexpectedly finding the virus in their backyard,” Lubroth said.
The countries where H5N1 is still firmly entrenched – Bangladesh, China, Egypt, India, Indonesia and Vietnam – are likely to face the biggest problems but no country can consider itself safe, he said.
“Preparedness and surveillance remain essential,” Lubroth underlined. “This is no time for complacency. No one can let their guard down with H5N1.”