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OIE Warns of H5N1 Migration to North America and Australia
March 8, 2006
Australia, Canada and the United States stand a "very high" risk of seeing the current H5N1 bird flu pandemic spread to their shores, the Paris-based World Organisation for Animal Health (OIE) warned.
"The probability of this strain appearing in Australia is very high. The possibility is also very high for the United States and Canada," OIE Director General Bernard Vallat told a French parliamentary commission on the disease.
The above comments by OIE are consistent with sequence analysis of H5N1 in wild birds in Astrakhan as well as H5N2 in British Columbia. The United States is planning on dramatically increasing surveillance, which is long overdue.
Canada released some data on their surveillance of birds banded in southern Canada in August. The released data revealed an unexpectedly high frequency of H5 detection in young healthy wild birds. All reporting provinces had H5 and British Columbia 24% of the birds tested were positive. However, only a partial sequence of two of the genes from a farm duck H5N2 isolate has been released. The N2 sequence had a large number of polymorphism historically founding Asia, indicating wild birds had recently been shuttling N2 sequences (largely from H9N2) in Asia into North America.
Similarly, sequences from recent H5N1 isolates in Astrakhan identified a number of American polymorphisms, suggesting earlier H5N1 migration to northeastern Canada. The August testing in southern Canada may have been too early to detect H5N,1 but analysis of a full dataset could define migratory paths of bird flu from both northeastern and northwestern Canada.
Recent sequences fro H5N1 isolates in China show evidence of extensive recombination between wild bird sequences. Tree sparrow sequences were identified in waterfowl and domestic poultry in eastern China, especially Henan province. The extent of recombination varied from isolate to isolate or gene to gene ranging from about 1/3 of the gene down to a single nucleotide. The single nucleotide changes can be used to trace migration in the past, which can be used to trace future migrations.
The United States is planning a dramatic increase in surveillance in Alaska. However, Canada already has a database of sequences from 2005 isolates that include H5N1, H5N2, H5N3, and H5N9 isolates. Release of these sequences would greatly enhance surveillance reports.
Similarly, WHO affiliated labs at Weybridge have sequestered a large number of sequences from H5N1 isolates throughout Europe. Release of these sequences would also greatly enhance analysis.
WHO and consultants are monitoring sequences for reassortment and "random mutations" which they maintain are not predictive. However, the "random mutations" are largely recombinations and are very predictive. WHO should release the sequences so they can be fully analyzed.