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Tests Equivocal on Qinghai H5N1 Cluster in Lagos Nigeria
January 30, 2007
"The tests we ran yesterday produced inconsistent results," said David Olaleye, who is taking part in the testing at a laboratory in the capital Abuja.
Olaleye said two initial rounds of tests over the weekend had proved negative but results from Monday's third round of tests had produced a pattern that was "unreliable" and did not allow him to make a clear call on the outcome.
"That is why we have pulled out a fresh batch of samples from the same people and we have started a completely new set of tests," he said.
The above comments raise concerns on H5N1 in patients in Nigeria. H5N1 false negatives are common. The above comments suggest that a third test of samples from three patients and contacts has produced a positive result. Prior media reports indicated that influenza A was confirmed in the three fatal cases, and an alternate serotype has not been described.
Recent reports indicate that H5N1 in Nigerian poultry is widespread. The re-emergence in Nigeria parallels the re-emergence in Egypt, which has reported human cases this season and last season.
All H5N1 in Europe, the Middle East, and Africa is the Qinghai strain (Clade 2.2). Several polymorphisms in Egyptian isolates are also in Nigerian isolates. Moreover, wild birds that migrate through Egypt winter in western African countries. Last season H5N1 was confirmed in Nigeria, Niger, Ivory Coast, Burkino Faso, and Cameroon in western Africa. Similarly, H5N1 was in African countries neighboring Egypt (Sudan and Djibouti), but a human infection was only reported in Djibouti.
Recent cluster members in Egypt had the Tamiflu resistance polymorphism, N294S. This marker was present in samples collected prior to Tamiflu treatment, raising concerns that N294S is circulation in Qinghai H5N1 in migratory birds.
More information on the testing of patients and birds in Nigeria would be useful.