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24 December 2008 - United States CDC issues interim recommendations for the use of influenza antiviral medications

The Centers for Disease Control and Prevention (CDC) today issued interim recommendations on the use influenza antiviral medications in light of preliminary data indicating a high prevalence of oseltamivir-resistant influenza A (H1N1) viruses.   CDC recommend that zanamivir or a combination of oseltamivir and rimantadine are more appropriate options than oseltamivir alone when influenza A (H1N1) infection or exposure is suspected.

The detailed recommendations are available at: http://www2a.cdc.gov/HAN/ArchiveSys/ViewMsgV.asp?AlertNum=00279


21 November 2008 - Oseltamivir-resistant influenza A (H1N1) virus in the UK, 2008/09 - an update

The Health Protection Agency today provided an update on the number of oseltamivir-resistant influenza A(H1N1) isolates detected in the UK during the 2008/09 season. From week 36/08 to 19th November, 12 of the 13 influenza A (H1N1) isolates detected in England have been found to be resistant to oseltamivir. Two oseltamivir resistant influenza A(H1N1) cases have also been detected in Scotland. All the H1N1 cases from England remain sensitive to zanamivir and amantadine and are antigenically similar to the H1N1 reference strain A/Brisbane/59/2007, which is included in this season's influenza vaccine.

Further information is available at: http://www.hpa.org.uk/hpr/archives/2008/news4708.htm#ah1n1


31 October 2008 - Encouraging results in clinical trials of antiviral drug, peramivir

BioCryst Pharmaceuticals Inc. reported encouraging results this week in two phase 2 trials of its injectable antiviral drug, peramivir, a potential new treatment for influenza. Peramivir is a neuraminidase inhibitor, like the licensed antivirals oseltamivir (Tamiflu), which is taken orally, and zanamivir (Relenza), inhaled as a powder.

In one study, a single intravenous (IV) dose of peramivir in outpatients ill with flu reduced the duration of their symptoms by about 22 hours compared with a placebo group, a statistically significant difference, according to BioCryst, based in Birmingham, Alabama, USA.  In the other trial, hospital patients who were seriously ill with flu were treated for 5 days with either IV peramivir or oseltamivir, with similar results in both groups, including no deaths and a median of 4.0 days to hospital discharge, the company said.

Neither set of results has yet been published in a peer-reviewed journal. The company described the inpatient study in a press release and a teleconference on Oct 27; the outpatient study was reported in an Oct 28 press release and a poster presentation at the 46th Interscience Conference on Antimicrobials and Chemotherapy/Infectious Diseases Society of America (ICAAC/IDSA) meeting in Washington, DC.

The new findings come 13 months after the company reported disappointing results in an earlier phase 2 trial of the drug. In that study, flu patients who received injections of peramivir did better than a placebo group, but the difference was not significant. The company said at the time that the use of shorter needles than were used in an earlier trial probably resulted in inadequate doses.


27 October 2008 - United States Centers for Disease Control report data on oseltamivir resistant viruses during 2007-08 season

Speaking at the 48th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC), Dr. Nila Dharan of the Centers for Disease Control and Prevention (CDC) disclosed that 12.6% (142 of 1,124) of H1N1 isolates sent to the CDC from around the United States during the 2007-08 season were resistant to oseltamivir, versus less than 1% before 2007. Additionally, the CDC found that none of the patients who gave the isolates had taken oseltamivir, casting doubt on the widely held belief that oseltamivir resistance, when it occurs, is not transmissible.

1. (Dharan NJ, Gubareva L, Klimov A, et al. Oseltamivir-resistant influenza A [H1N1] in the United States, 2007-2008 [Abstract V-918]).


04 October 2008 - UK Health Protection Agency report first oseltamivir-resistant influenza A (H1N1) virus for 2008/09 season

The Health Protection Agency today reported identification in the UK of the first oseltamivir-resistant influenza A(H1N1) virus of the 2008/09 season. Since week 34/08, several sporadic, laboratory-confirmed influenza infections have been detected in the United Kingdom (UK): isolates have included influenza A(H3N2), A(H1N1) and influenza B.

The first oseltamivir resistant influenza A(H1N1) for the 2008/09 season has also been identified in the UK through the HPA sentinel GP virological surveillance scheme. The virus contains the H274Y mutation but remains sensitive to zanamivir and amantadine, and is antigenically similar to the H1N1 reference strain A/Brisbane/ 59/2007, which is included in this season's influenza vaccine.  Antiviral susceptibility tests on A(H3) isolates showed that they are sensitive to oseltamivir and zanamivir.  Further information is available at: http://www.hpa.org.uk/hpr/archives/2008/news4308.htm#ah1n1


05 September 2008 - Scientific report on death of leukaemia patient infected with oseltamivir-resistant influenza A(H1N1)

In a letter to the New England Journal of Medicine (NEJM) (week ending 31 August), Dutch authors reported the death of a leukaemia patient who was infected with an H1N1 virus that was resistant to oseltamivir. Available at: http://content.nejm.org/cgi/content/full/359/10/1074

The authors said the case suggests that oseltamivir-resistant H1N1 viruses can cause disease, despite evidence from animal studies that the resistance mutation makes the viruses much less dangerous. The letter said the man's virus was also resistant to amantadine, an older antiviral drug. It is not yet clear if the increased pathogenesis of the virus that fatally infected this patient was due to its improved fitness or to the immunocompromised state of the patient himself.


20 August 2008 - World Health Organisation update on oseltamivir-resistant influenza A(H1N1)

Data released by the World Health Organisation (WHO) on 20 August 2008 indicate that 242/788 (31%) influenza A H1N1 isolates tested showed the specific neuraminidase mutation (H274Y) associated with oseltamivir resistance.  Data, summarised by WHO region, are available on the WHO website.  The WHO will continue to update a summary table on a monthly basis, unless the situation changes, and are continuing to monitor the situation.


30 January 2008 - Virgil Network reports indentification of oseltamivir-resistant influenza A(H1N1)

In late January 2008, antiviral drug susceptibility surveillance of seasonal influenza viruses was carried out by the EU-funded VIRGIL network. Results of this surveillance revealed that some of the A (H1N1) viruses circulating during winter 2007-8 were resistant to the antiviral drug oseltamivir through mutation at position 274 in the viral neuraminidase gene.

Read the European Centre for Disease Control (ECDC) Interim Risk Assessment

Read Eurosurveillance articles on the emergence of influenza viruses resistant to the antiviral drug oseltamivir: