#4998
That the novel H1N1 virus would begin to show signs of changing over time comes as no surprise. Indeed, many experts expected to see changes begin last fall and winter in the northern hemisphere, and were surprised at how stable the virus remained.
Small changes were detected, in what appeared to be widely scattered mutations.
The D22G – or Norway mutation – garnered a good deal of press beginning in November of 2009. It failed, however, spread widely and in any event, the feared pathogenic changes that came with that mutation were inconsistent.
Some cases were more severe, while others remained mild. For more, see:
Study: Receptor Binding Changes With H1N1 D222G Mutation
CIDRAP Report On The H1N1 Mutation Debate
WER Review: D222G Mutation In H1N1
Similarly, a relative handful of H275Y mutations which conveyed Oseltamivir resistance have been reported. But once again, there was little evidence to suggest it was spreading widely.
NIH: Rapid Development Of Antiviral Resistance In Two Cases
WER Review: Oseltamivir Resistance In Pandemic H1N1
So called `low reactor’ viruses – those that appeared to be less well matched to the current pandemic H1N1 component to the flu vaccine – have also been reported in a few scattered instances around the world.
But overall, the virus has remained antigenically close to the A/California/7/2009-like strain included in the vaccine.
Today Eurosurveillance has a major report on the detection of a growing number of `drifted’ H1N1 virus isolates from Singapore, Australia, and New Zealand over the winter of 2010.
The important points here are that right now, despite some reported vaccine `breakthroughs’ and some reported fatal cases with this mutation, it doesn’t appear that these changes render the existing vaccine ineffective, and pending further information there is scant evidence that they make the virus more dangerous.
A less positive note is that this `mutated’ virus appears to be relatively biologically `fit’, and capable of competing with the original virus, and spreading throughout the human population.
What this does tell us is that the virus is picking up changes, and that it must be closely watched as it slowly evolves during its run in through the northern hemisphere.
Eurosurveillance, Volume 15, Issue 42, 21 October 2010
Barr IG, Cui L, Komadina N, Lee RT, Lin RT, Deng Y, Caldwell N, Shaw R, Maurer-Stroh S. A new pandemic influenza A(H1N1) genetic variant predominated in the winter 2010 influenza season in Australia, New Zealand and Singapore. Euro Surveill. 2010;15(42):pii=19692.
Date of submission: 14 September 2010
Pandemic H1N1 influenza virus is of global health concern and is currently the predominant influenza virus subtype circulating in the southern hemisphere 2010 winter. The virus has changed little since it emerged in 2009, however, in this report we describe several genetically distinct changes in the pandemic H1N1 influenza virus.
These variants were first detected in Singapore in early 2010 and have subsequently spread through Australia and New Zealand.
At this stage, these signature changes in the haemagglutinin and neuraminidase proteins have not resulted in significant antigenic changes which might make the current vaccine less effective, but such adaptive mutations should be carefully monitored as the northern hemisphere approaches its winter influenza season.
The always dependable Maggie Fox, science and health editor of Reuters, has a report on all of this which you can access at:
New strain of swine flu emerges - report
Maggie Fox, Health and Science Editor
The bottom line: The impact of these mutational changes is unclear at this time, but this reinforces the need to monitor the antigenic changes of this – and any other – circulating flu virus.
