Spread of the virus is entering an ` ` acceleration phase , '' official says . Countries will see a surge of cases every three to four days , he says . More than 1,490 people have died from the virus since last year . H1N1 is the first influenza outbreak in more than 40 years .
Spread of the virus is entering an `` acceleration period , '' official says . Countries may see a doubling of cases every three to four days , he says . More than 1,490 people have died from the virus since last spring . H1N1 is the first influenza pandemic in more than 40 years .