Kolkata, Aug 13 - The number of confirmed swine flu cases in West Bengal rose to 18 Thursday, as five more people have been detected with the H1N1 virus infection in the state.

'We've received five fresh cases today (Thursday). All of them have been admitted to the Beliaghata Infectious Diseases (ID) Hospital here,' Tapas Sen, the state's nodal officer for swine flu, told IANS.

'All of them underwent tests after displaying symptoms of the infection and they have been detected positive,' he said. Sen said eight other confirmed swine flu cases had already been discharged from the hospital after treatment.