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H5N1 Geographic and Genetic Evolution
November 12, 2005
The recent news on the genetic and geographical evolution of H5N1 points toward a dramatic expansion of the geographical reach of H5N1 couple with increased efficiency of infections in humans.
The geographical expansion began with detection in long range migratory birds at Qinghai Lake in May. The H5N1 identified had the characteristic multi-basic HA cleavage site of RRRKKR found exclusively in H5N1 HPAI from Asia. These sequences were soon detected in Russia, Kazakhstan, and Mongolia and reported for the first time in each country.
The cooler temperatures in these regions suggested the H5N1 would spread to Europe, the Middle East, and Africa and H5N1 detected in Romania, Turkey, Croatia, and Kuwait confirmed this prediction. The recent outbreaks in several provinces in China as well as fresh outbreaks in Vietnam, Thailand, and Indonesia indicated migratory birds were bringing in new sequences to there regions endemic for H5N1.
Coupled with the detection of the news sequences in the endemic region were reports of clusters of human cases. China has admitted for the first time that three victims in Hunan Province may have been infected with H5N1. Now there is a fourth suspect case, but in Liaoning Province. China has filed reports detailing four separate outbreaks. Although media reports have suggested that H5N1 control is hampered by use of fake or shoddy vaccines, the latest reports detail new immunizations with 3 different vaccine preparations, suggesting significant resistance to each individual vaccine.
Clearly H5N1 is rapidly evolving and previous control efforts are failing. Although China has promptly reported several recent outbreaks, sequences have not been made public since Qinghai Lake in May. Similarly, Thailand has only deposited 2 sequences from 2005 isolates and Indonesia has deposited none.
H5N1 is rapidly changing in many regions, and the exploding geographical reach suggests H5N1 will become endemic worldwide and new versions will appear with increasing frequency as the H5N1 recombines with regional isolates.
H5N1 is clearly gaining the upper hand, while reporting lags and false negatives accumulate.