# 4325
Concerns that the novel H1N1 virus could develop widespread Tamiflu (Oseltamivir) resistance - as did its seasonal cousin in 2008 & 2009 – have been the topic of much discussion in scientific circles since last April.
Thus far, it appears that the overwhelming majority of pandemic flu cases still respond to Tamiflu, although sporadic resistant cases have been seen. Testing is only done on a miniscule percentage of cases however, and so the actual incidence of resistance is unknown.
Resistance is generally caused by a mutation, known as H274Y, where a single amino acid substitution (histidine (H) to tyrosine (Y)) occurs at the neuraminidase position 274.
In the The World Health Organization’s latest (No. 6, 2010, 85, 37–48) Weekly Epidemiological Record (WER), we get an update on this mutation.
I’ve just reproduced some excerpts below. Follow the link to read the entire report. A Hat tip to Ironorehopper on FluTrackers for posting this link.
Update on oseltamivir resistant pandemic A (H1N1) 2009 influenza virus: January 2010
Since the first report of oseltamivir-resistant pandemic influenza A (H1N1) 2009 virus in June 2009, >200 cases of resistant virus have been reported worldwide. The purpose of this article is to provide a brief global update on cases of oseltamivir resistant pandemic (H1N1) 2009 viruses since the first report published in the Weekly Epidemiological Record2 in October 2009.
With the exception of the 225 cases summarized here, all clinical samples tested for pandemic (H1N1) 2009 virus lack the H275Y mutation and are therefore assumed to be sensitive to the influenza virus neuraminidase inhibitors oseltamivir and zanamivir. While this indicates the absence of wider community circulation of oseltamivir-resistant virus, recently reported clusters of cases suggest that such viruses are being transmitted in local settings.<SNIP>
Conclusions
The number of reported cases of oseltamivir-resistant pandemic (H1N1) 2009 influenza virus remains low despite the large scale of the pandemic, widespread use of oseltamivir and extensive monitoring of susceptibility. Although there is no evidence of general community circulation of such resistant viruses, there is clear evidence of limited person-to-person transmission in several epidemiological settings. Active surveillance for antiviral resistance in pandemic (H1N1) 2009 virus needs to be maintained by clinicians, laboratories and agencies. All cases of oseltamivir-resistant pandemic A (H1N1) 2009 influenza virus should be investigated and promptly notified to relevant agencies including WHO.
