Five patients on a unit treating patients with severe underlying health conditions at the University Hospital of Wales, Cardiff, have been diagnosed with swine flu resistant to Tamiflu. It is believed that the patients acquired the infection in hospital.

Dr Roland Salmon, director of the NPHS Communicable Disease Surveillance Centre, said: ‘The emergence of influenza A viruses that are resistant to Tamiflu is not unexpected in patients with serious underlying conditions and suppressed immune systems, who still test positive for the virus despite treatment. 

‘In this case, the resistant strain of swine flu does not appear to be any more severe than the swine flu virus that has been circulating since April.

‘For the vast majority of people, Tamiflu has proved effective in reducing the severity of illness.'

Vaccination remains the most effective tool we have in preventing swine flu so I urge people identified as being at risk to look out for their invitation to be vaccinated by their GP surgery, added Dr Salmon.