UK Rise in Neuraminidase Inhibitor Anti-Viral Drug Resistance

The UK HPA Weekly National Influenza Reports covering the emerging epidemic from the past two weeks (Week 51 and Week 52) provide insight into data scarcity surrounding anti-viral drug resistance.

Oseltamivir-resistance may be determined genetically from a Single Nucleotide Polymorphism (SNP) H275Y on the Neuraminidase. Clinical anti-viral resistance and / or ineffectiveness in Pandemic H1N1 Influenza continues to manifest much more widely than can be attributed to the genetic variance of NA 275Y.  In the future, other factors may be identified as genetically leading to the clinical manifestations in cases that do not demonstrate H275Y, but for the moment, the measurement is at that single change.

The HPA Week 51 data reported 3 TmX cases from 402 tested (~0.75%).
The HPA Week 52 data reported 5 TmX cases from 336 tested (~1.49%).

As you can see, the percentage of resistant cases week over week increased by 99%.  Unfortunately, data sparsity alongside the fact of taking percentages of percentages may not allow this figure to be fully reliable for decision-making.

On the other hand, in a crisis when faced with limited testing capacity and limited testing foundation, these are the types of acceleration / deceleration calculations that must be made. Data that is available is used. GeneWurx would like to see clinical meta-data paired with genetic sequences to assist in pinpointing various HA polymorphisms that may also be associated with drug resistance, such as those trailing HA aa500.

GeneWurx has prepared an Excel spreadsheet so that the public may track any ongoing official and / or unofficial data concerning Anti-Viral resistance patterns.


Bear in mind that a recent seasonal influenza rapidly progressed from Anti-Viral sensitivity to Anti-Viral resistance across the world in less than one full season when the percentage of strains demonstrating NA H275Y reached approximately 2%.

More than 100 drug-resistant human Pandemic H1N1 sequences are on file considering just North America and Asia.  Washington01_2010_04_02_TmX from the United States registered with 33 polymorphisms across the HA and NA gene segments.  In August 2010, GeneWurx evaluated 7 sequences from Japan with extensive HA diversity and H275Y TamiFlu Resistance

With drug resistant, hypermorphic strains carrying shared HA polymorphisms now being documented across a wide geography, will the resistant 2% begin to spread in Winter 2010-2011?

Please visit GeneWurx.com for insight into the latest published studies. GeneWurx.com