The World Health Organisation (WHO) said today that Tamiflu resistance in some H1N1 patients with badly weakened immune systems does not seem to reflect a major change in the virus' susceptibility to the frontline drug. 

The world health body’s flu expert Keiji Fukuda said nine people in Britain and the United States developed a Tamiflu-resistant form of swine flu while being treated in hospital mainly for blood cancers. 

"We don't know the full answer. But it is more likely that we are not seeing a change, a major shift in the epidemiology or in the properties of these viruses with regard to oseltamivir resistance," he told a weekly news conference. He said Tamiflu, known generically as oseltamivir and made by Switzerland's Roche, was effective when used correctly and early. 

About 75 cases of oseltamivir-resistant viruses have been reported worldwide in recent months, mostly isolated cases which have arisen after preventive treatment with the drug, he said. 

"Right now we do not see any evidence of a large impact in immuno-compromised people with milder forms and we do not see a large impact in HIV-infected populations," he said. Swine flu is expected to infect more people in the northern hemisphere in the next weeks before there is a downturn, but is less prevalent in the southern hemisphere, Fukuda said. - Reuters