Health officials at a hospital in Wales are investigating a possible person-to-person spread of a drug resistant strain of H1N1 flu.Five patients are confirmed to have a variant of the virus. The cases occurred in people with underlying health conditions known to provoke a resistance to the anti-viral drug Tamiflu. But three appear to have acquired the infection in hospital. Worldwide there are 57 Tamiflu resistant cases but if confirmed this is the first time one person may have infected another. The patients in Cardiff are responding to treatment with alternative anti-viral drugs. Meanwhile Norwegian health authorities have discovered a further potentially significant mutation of H1N1. Three people are said to have developed a strain causing more severe symptoms among those infected. However, The World Health Authority says there is no evidence to suggest any reduction in the effectiveness of the flu vaccines or drug treatments.