Resistance to the anti-flu drug oseltamivir has been noted in both the 2007-8 and 2008-9 flu season in the United States. Indeed, the resistance appears to be increasing, highlighting the need for more research and more self-help in dealing with influenza.

Summary

The Centers for Disease Control and Prevention have carried out analyses of flu viruses from last year's and this year's flu season. Among H1NI strains, 12% were resistant to a common flu drug in 2007-8 and by this year, this had gone up to 98%. The findings underscore the need to keep looking for new flu drugs and to do all we can to stop the spread of the virus.

Introduction

Influenza is notorious for its ability to mutate and so evolve resistance to the drugs and vaccines we use to protect ourselves. Tamiflu or oseltamivir is a drug that can be used to reduce the symptoms and duration of a bout of influenza. There is much discussion about creating stockpiles of Tamiflu ahead of a potential influenza pandemic. Therefore, it's important to keep an eye open for influenza strains that might be developing resistance to this drug.

What was done

Researchers at the Centers for Disease and Control (CDC) in the United States carry out ongoing analysis of flu viruses. They have sampled viruses from patients infected with influenza in the 2007-8 and in the current 2008-200 flu season.

What was found

During the 2007-8 flu season, increased levels of resistance to oseltamivir were detected both in the US and around the world. The H1N1 strain accounted for 19% of circulating viruses in the US of which 12% proved to be resistant to the drug. Among the resistant cases, 5% had to be hospitalized and 4% died - so this strain is a serious public health issue. However, there were no significant differences between patient demographics or the symptoms between cases of oseltamivir-resistant and oseltamivir-susceptible cases. By the current flu season, resistance to oseltamivir was being detected in as many as 98.5% of US H1N1 samples tested.

What this study means

The findings confirm that it will not be possible to rely on just Tamiflu as protection against flu - whether it be the regular seasonal kind or a pandemic. Other anti-viral drugs are needed. It is also important not to forget the self-help approach to flu - social distancing, if you have the infection, frequent hand-washing and vaccination where appropriate.

Source

Infections with oseltamivir resistant influenza A (H1N1) in the United States NJ. Dharan, LV. Gubvera,  et al, Journal of the American Medical Association, March 11 2009, vol. 301, pp. 1034--1041