# 1556
About 2 years ago, the medical community was shocked to find that an old standby antiviral, amantadine, had lost much of its effectiveness against the H3N2 virus. In 2003, roughly 1.9% of viruses tested showed resistance, in 2004 that jumped to 9%, and by 2005 a full 91% were resistant.
Overuse of the drug (it was rumored to have even been used in chicken feed in Asia to ward off bird flu) rendered it useless. A shame because Amantadine (and rimantadin, also compromised) was not only cheap, it was plentiful.
The CDC, in January of 2006, warned doctors to no longer prescribe it for seasonal influenza.
Tamiflu has, up until now, shown little signs of losing sensitivity for seasonal flu viruses. There have been a few cases in Egypt and Vietnam where the H5N1 virus has proven resistant, but for the most part, seasonal flu still responded to the treatment.
Now, a new study indicates that for the first time, researchers are seeing a few cases of Tamiflu resistance in seasonal flu. Not a lot, but some.
This from Reuters.
Tuesday January 29, 07:09 AM
Some ordinary flu strains resist Tamiflu in study
STOCKHOLM/ZURICH (Reuters) - Some seasonal influenza viruses are resistant to Roche Holding AG's Tamiflu, a study showed, but Roche said no doubts had been raised about the drug's power to combat any deadly bird flu pandemic.
Of 148 samples of influenza A virus isolated from 10 European countries during November and December, 19 showed signs of resistance to Tamiflu, the European Centre for Disease Control said on Monday, citing a preliminary survey.
Of 16 samples from Norway, 12 tested positive for resistance against Tamiflu, which is also known by the generic name oseltamivir, Stockholm-based ECDC said.
"Given the initial indication of a high level of resistance to oseltamivir in the A H1N1 viruses circulating in Norway, late last week ... the Norwegian authorities notified their EU partners and the World Health Organization (WHO) of this situation," the ECDC said.
Roche points out that this is an extremely small sampling, and that this does not indicate any loss of effectiveness against the H5N1 strain.
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