Flu cases rise on west coast earlier than usual as US health experts encourage vaccine

California flu test rate at 9.65%, higher than normal 1% rate for early October, amid mutation of H1N1 influenza A strain

Flu cases on the west coast are on the rise months earlier than normal, prompting US health experts to stress the importance of the annual vaccine.

Flu activity typically ramps up in December, hitting its peak in February. But this season has kicked into action earlier this year, with higher positive cases than normal recorded.