TOKYO - A GENETIC mutation of H1N1 flu that is resistant to the anti-viral Tamiflu has been discovered in Japan, the first such case in the country, the health ministry said.

It was the second reported case of Tamiflu resistance linked to H1N1 flu in less than a week.

The latest case was found in a patient who had been given the drug since first being diagnosed with A(H1N1) around two weeks ago, Kyodo news agency reported on Thursday, citing the Health, Welfare and Labour Ministry.

The patient - a woman in Osaka prefecture - was recovering after having been given Relenza, an alternative anti-flu medication, the report said.

A spokesman for Swiss pharmaceuticals giant Roche, which makes Tamiflu, said the company had been informed of the case and called it 'normal.'

'It is absolutely normal,' she said, adding that '0.4 per cent of adults develop resistance' to Tamiflu.

She said the case does not indicate Tamiflu has become less effective against H1N1 flu.

Danish authorities announced earlier this week they had discovered resistance to Tamiflu in a female patient. Relenza was also used successfully to treat her.

According to the latest World Health Organisation figures, Japan has 1,266 reported cases of swine flu, but has so far recorded no fatalities. -- AFP