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Bird Flu Recombinants in Patients In Vietnam?
January 22, 2005
>>Tran Tinh Hien, deputy director of Ho Chi Minh City's Hospital of Tropical Diseases, told AFP "she was tested positive Friday evening to type-A avian flu".
The only strain of avian flu recorded in the country is the H5N1 strain……….
The test results on the two deaths are not affirmative, not clear yet," institute director Nguyen Thi Kim Tien old Reuters, adding that more tests were being done. <<
The two statements above may not be contradictory. If the H and N are changing via recombination, the sub-typing sera may not be reacting this season as it reacted to last season's H5N1. Therefore the comment on the broader tests (type-A avian flu) may not translate to subtyping results (positive for H5N1).
Thus, the statements last night from two officials of the same institution commenting on the same two fatal cases, may not be contradictory, and may provide additional evidence that difficulties detecting H5N1 is due to the fact that the type A influenza in the north and south are recombinants.
Recombinants are a major concern because they can combine a human receptor binding domain with additional H5 avian sequences to create a virus with high virulence and increased human transmissibility. Such recombinants can also generate negative results for older sub-typing reagents.
These "false negatives" may apply to other areas. Although Thailand is reporting increased detection of H5N1 in birds this year, reported results on suspect human cases this season have been negative. Reports on the "influenza A" status of these patients would be useful.
More information on the specific tests yielding negative and positive results in Vietnam, as well as sequence information on the new isolates, would also be helpful.