Monday, February 07, 2011

Korea: Migratory Birds Behind Spread Of H5N1




# 5294



While their conclusions are hardly a surprise given the number of infected migratory birds detected this year, from Yonhap News Agency this morning we get official statements on how the worst outbreak of H5N1 bird flu in Korea’s history has been spread.


Since November, both Korea and Japan have reported an unusually high number of H5N1 infected migratory birds, which authorities believe have reintroduced the virus into the nation’s commercial poultry.


The latest Korean numbers have 40+ farms with infections, and in excess of 5.4 million birds culled.   This exceeds the size and scope of their  April 2008 outbreak, with still a 2 or 3 more months of prime `bird flu season’ left to go.


All of this comes amid the worst outbreak of FMD (Foot and Mouth Disease) in South Korea’s history, requiring the destruction of more than 3 million pigs, cattle, sheep, and goats since November of 2010 (see South Korea Battles Bird Flu, FMD).


Japan and Korea are both part of the great East Asian - Australasian Flyway, and are the winter home for many species of migrating birds, many of which spend their summers in Siberia, China, and Mongolia. 





Today’s report quotes Joo Yi-seok, from the National Veterinary Research and Quarantine Service, as saying:


"Direct contact with infected wild birds and indirect contamination caused by people and vehicles stepping on bird droppings may have triggered 22 of the confirmed cases, with the rest involving the virus being spread inadvertently by contaminated bird feed and rice husks used in coops.”


Here’s the link to the Yonhap report.


2011/02/07 14:06 KST

Migratory birds trigger AI outbreak: gov't



After the initial spread of clade 2.2 of the H5N1 virus out of Qinghai Lake in 2006 to Europe and Africa and the rest of Asia, we saw a gradual reduction in the number of wild bird die offs around the world.


In 2007, it was even suggested by some OIE  researchers that the H5N1 virus might be on the wane in the wild (see Avian Flu Nearing End Of It's Cycle?).


But the H5N1 virus isn’t a single entity.  It is a collection of at least a half dozen different clades – each capable of independently mutating, changing, or adapting over time.  


And so - while the incidence of some clades may subside - others may rise.


Bird flu reports began to pick up again in 2008 and 2009, notably in Japan, Korea, Bangladesh, and India. Talk of the virus being in decline was quickly forgotten.


After another lull in reporting over 2009-2010, H5N1 is once again back in the news.


Whether the virus was really less active during that time, or our attention was simply diverted by the H1N1 pandemic, is hard to know.  


But what is obvious is that while there may be some cyclical pattern to outbreaks, the HPAI avian flu virus continues to be endemic in wild birds (particularly in China and Siberia), and is reasserting itself in countries that have managed to avoid it for nearly 3 years (see What Goes Around, Comes Around).


For now, the H5N1 virus is primarily a threat to wild birds, poultry and agricultural interests - and to a lesser extent - those who are in close contact with birds.


The virus remains poorly adapted to human physiology, and very difficult to catch.  Rarer still are cases where the virus spreads from one person to another.


But of course, the concern is that could change over time.


And so the world remains at Pre-pandemic Phase III on the H5N1 virus, and we continue to watch for any signs that the virus is adapting to humans.

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