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H5N1 Bird Flu In Maryland
September 1, 2006
Mallard ducks in Maryland have tested positive for bird flu, apparently a common, less pathogenic strain that poses no risk to humans, the U.S. Agriculture and Interior departments said on Friday.
The H5N1 avian influenza virus was found in fecal samples from "resident wild" mallards in Queen Anne's County in Maryland, on the U.S. central Atlantic coast.
"Testing has ruled out the possibility of this being the highly pathogenic H5N1 strain that has spread through birds in Asia, Europe and Africa,"
The detection of H5N1 in Maryland is not a surprise. H5N1 was recently detected in Michigan and comments indicated that sequence data showed in was a low path North American version. The above comments suggest that the HA cleavage site has already been sequenced and the positives in Maryland are also low path.
In August, 2005, Canada swabbed mallards from coast to coast in southern Canada. Detection of H5 was common (H5N1, H5N2, H5N3, H5N9 were detected). H5N1 was in Manitoba and the positive results in southern Michigan on the shores of Lake Erie suggested that widespread detection of H5N1 in the United States was likely. Moreover, H5 was detected in a dead goose on Prince Edward Island, suggesting high path H5 is also in North America.
Thus far, only one sequence from the 2005 isolates in Canada has been published. The sequence indicate the H5 had acquired polymorphisms found in swine in Canada and also had a polymorphism found in high path H5N1 in Indonesia. These data indicate that low path H5 can serve as donor or recipient of mammalian or H5N1 sequences. Similar links to North America have been found for the high path H5N1 Qinghai strain of bird flu. In addition, H5N1 in Asia have polymorphism that trace back to low path H5 in Asia.
Thus, although the detection of H5N1 in Michigan and Maryland do not pose a direct threat, the genetic information in these low path H5N1’s can easily transfer to high path H5N1 via recombination.
Release of sequence data on the H5N1 in Michigan and Maryland would be useful. More H5N1 in the United States and Canada is expected, and these positives are likely to be both low and high path H5N1, since wild birds readily transport and transmit both versions and the H5 on Prince Edward Island was propably the Qinghai nstrain of H5N1.