Scientists have warned that vulnerable patients may be at risk of contracting a drug-resistant 'super-flu'.
According to research in the Journal of the American Medical Association (Jama), the H1N1 A virus, which is a strain that causes common flu outbreaks, carries an altered gene that makes it resistant to the anti-viral drug oseltamivir.
The drug, which is sold as Tamiflu, is used as one of the first lines of treatment to protect people who are most vulnerable to flu, such as older people. But a group of Dutch doctors have identified the emergence of Tamiflu-resistant flu in the Netherlands and US.
Led by Dr Jairo Gooskens, from Leiden University Medical Centre, the doctors have warned that there has been a rapid spread of resistant H1N1 flu strains since January 2008.
It was previously thought that the gene mutation, labelled H274Y, was less virulent and less easily transmitted, but researchers say it retains transmissibility.
The Dutch researchers wrote: 'Current widespread circulation of oseltamivir-resistant influenza A (H1N1) viruses associated with typical influenza illnesses and viral pneumonia suggest that these viruses retain significant transmissibility and pathogenicity.'
The authors said the findings show that the introduction of 'new and effective antiviral agents and therapeutic strategies' is necessary.
Related article: A jab 'to cure all flu'?
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