H5N1 Reservoirs West of China
Recombinomics Commentary 20:40
January 10, 2008
But Bernard Vallat, director general of the World Organisation for Animal Health (OIE), said no evidence of any such genetic shift had emerged.
"We have never seen a virus which has been so stable for so long. Compared to other viruses, it is extremely stable, which minimises the risk of mutation" into a pandemic strain, he told reporters.
Vallat said, though, "there are three countries, Indonesia, Egypt and to a lesser degree Nigeria, where the disease is endemic, and this creates reservoirs from which it can bounce back."
"If we could eradicate the virus in those countries, the problem of a pandemic from Asian H5N1 would be resolved," said Vallat.
The above comments are alarming. Although many H5N1 sequences are still being hoarded, the overall evolution of the virus is quite clear and indicates it is not dependent on reservoirs in the above countries. In fact prior to 2006, neither Egypt nor Nigeria had ever reported a case of H5N1. The first reported outbreak of H5N1 west of China was in late 2005, which was linked to the Qinghai strain (clade 2.2) of H5N1, which has now become endemic throughout Europe, the Middle East, and Africa. The dramatic spread in geographical reach was due to migratory birds, which pass through Egypt and Nigeria, but are not dependent on reservoirs in those two countries.
The H5N1 sequences demonstrate geographic origins and clade 2.2, which spread from the largest lake in China, has now been replaced by the Uva Lake strain (a clade 2.2 sub-clade), which spread from the largest lake in Mongolia. Every reported H5N1 sequence in Europe since the summer of 2007 has been the Uva Lake strain, and there have not been any reports of that strain in Egypt or Nigeria. The most recent sequences available from those countries have been the Qinghai strain.
The reservoir for H5N1 is wild birds, which are largely immune from efforts by FAO or OIE. The latest outbreak, in wild birds, was announced today in England. An explosion of cases is expected this winter, based on the dramatic upsurge in outbreaks this summer and fall in the Czech Republic, Germany, France, Russia (Krasnodar and Rostov), Poland, Romania, Saudi Arabia, Israel, and Egypt. The European and Middle Eastern countries not mentioned above will report H5N1 in the near term, if they have a modern surveillance program.
H5N1 is more widespread than ever, OIE speeches and press releases notwithstanding.
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