The HSE has had no reports of any cases of Tamiflu-resistant swine flu in Ireland but says it is monitoring the situation closely. This follows reports yesterday that five patients at a Welsh hospital have been diagnosed with a strain of swine flu which is resistant to the antiviral.

Such a development would be significant if, as suspected, they turn out to be the world's first confirmed cases of person-to-person transmission of this more virulent strain.

A HSE spokeswoman said health practitioners in Ireland have been using the antiviral drug Tamiflu only to treat "at risk" or severe cases of swine flu.

"It doesn't get rid of the virus but it does make it less unpleasant and reduces the risk of complications," she said. "We haven't been using it in the vast majority of cases as the UK has been."

The Welsh cases occurred in patients with haematological problems who had compromised immune systems.

Three of the five people diagnosed with Tamiflu-resist­ant swine flu in a unit for patients with severe underlying health conditions appear­ to have acquired the infection on the ward, according to UK health authorities.