Danish health officials on Monday reported the first case of resistance to Tamiflu, considered to be the most effective treatment for swine flu by the World Health Organization.
The Danish national is no longer suffering from the illness and is not displaying symptoms, the Danish Institute of Serology said in a statement.
The patient had been in direct contact with a swine flu victim and so was given a dosage of Tamiflu as a preventative measure.
But she still contracted the virus after her body resisted the treatment, leading doctors to give her another type of medication, Relenza, made by British pharmaceutical giant GlaxoSmithKline.
Nils Strandberg, the institute's director, said he was satisfied with the methods used to monitor swine flu, adding that "the spontaneous mutation of a flu virus is not unusual".
He refused to rule out new mutations of the virus appearing in the future and stressed this case posed no risk to public health or the recommendations on the use of Tamiflu.
Case of swine flu treatment resistance 'expected': Roche
Swiss drugs company Roche said Monday that a swine flu patient's resistance to treatment with its Tamiflu drug in Denmark was expected and likely to be an individual case.
"This was very much expected," said David Reddy, Roche's pandemic task force leader.
"It doesn't mean the circulating virus is resistant to Tamiflu," he told AFP.
Danish health officials on Monday reported the first case of resistance in a patient treated with Tamiflu, an antiviral drug that is one of the key influenza treatments recommended by the World Health Organization.
The Dane is no longer suffering from the illness and is not displaying symptoms, the Danish Institute of Serology said in a statement.
Reddy said the case was within the 0.5 percent rate of case resistance to Tamiflu established in clinical trials.
Other people also infected with the Dane were treated with Tamiflu, and Reddy suggested it showed that the individual patient had some form of resistance rather than the A(H1N1) influenza virus.
The patient was given another type of medication, Relenza, made by British pharmaceutical giant GlaxoSmithKline.
(c) 2009 AFP
Explore further: Health officials warn of Sea-Tac measles exposure