Japanese has detected the first genetic mutation of the new H1N1 strain of influenza A that develops resistance to the anti-flu drug Tamiflu, the health ministry said late on Thursday.

The Tamiflu-resistant virus was detected in a woman in her 40s infected with the new influenza in Osaka Prefecture, it said.

The ministry added she is already recovering after being administered Relenza, another anti-flu drug.

The female patient had been administered Tamiflu since May 18 as a preventive measure after she was found to have had close contact with another confirmed infected patient the previous day.

She was confirmed infected with A/H1N1 influenza on May 28. An analysis of a virus taken from her detected the genetic mutation that does not respond to Tamiflu on June 18.

The first case of HINI that showed resistance to Tamiflu was reported in Denmark at the end of last month.

(Xinhua News Agency July 3, 2009)