Commentary
100% H1N1 Tamiflu Resistance in Australia and South Africa
Recombinomics Commentary 21:44
August 21, 2008
In South Africa, a total of 139 A(H1N1) viruses have been isolated during the 2008 influenza season to date.
Of those, 107 isolates have been tested for oseltamivir resistance by the National Institute of Communicable Diseases (NICD) and 100% were found to be resistant to oseltamivir by genotypic analysis.
From Australia, 10 of 10 A(H1N1) viruses tested, and from Chile, 4 of 32 A(H1N1) viruses tested showed the specific neuraminidase mutation (H274Y) associated with oseltamivir resistance.
The above comments suggest that Tamiflu (oseltamivir) resistance (H274Y) is running at 100% in South Africa and Australia, strongly suggesting that similar levels will be seen in the upcoming flu season in the northern hemisphere.
The latest update extends earlier results from South Africa, which included analysis of the first 23 isolates. All contained H274Y, which was confirmed by the release of 16 HA and NA sequences. The sequences fell into two sub-clades and one of the sub-clades had 5 clustered polymorphisms near the receptor binding domain position of 190 (H3 numbering). Three of these five changes were non-synonymous, raising concerns that the H1 was rapidly evolving away from the Brisbane/59 sequences, which are the target of the northern hemisphere vaccine, which will be released in the next few months. Moreover, the two polymorphisms from the 3’ side of the cluster matched H1N1 sequences from the 1940’s
The detection of H274Y in all 107 isolates sequenced, coupled with 100% in Australian isolates, indicates that those isolates with H274Y are becoming dominant. These sequences may be linked to recent reports of high frequency pneumonia levels in Zimbabwe.
More information of the severity of the H1N1 cases in South Africa and Australia would be useful.
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