The number of confirmed cases of swine flu in Japan soared on Monday, forcing the closure of thousands of schools in the western region worst hit and raising fears about the likely impact on an economy already suffering a historic slump.

The rapid spread of the new flu, with more than 130 cases of infection confirmed by Monday – from four before the weekend – showed that Japan’s attempt to block the virus at its borders had failed, prompting heated debate on efforts to limit its spread.