( CNN ) -- The number of confirmed cases of the H1N1 virus has jumped nearly 30 percent with 331 people being infected so far , the World Health Organization said Friday . A young couple in Mexico City wear surgical masks in an attempt to avoid contamination from the virus . The WHO added that the virus had spread to 11 countries , but the hardest hit areas were in the western hemisphere . `` We have not seen sustained human to human transmission anywhere outside the Americas region , '' said WHO spokesman Thomas Abraham . Two more countries , Denmark and China , reported cases of the 2009 H1N1 `` swine flu '' virus on Friday , but they were still to be confirmed by the WHO . The largest outbreak was in Mexico which had 156 confirmed cases , while there were 141 cases confirmed and one death in the United States , according to the Centers for Disease Control and Prevention ( CDC ) . The WHO said Mexico had 9 deaths attributed to the virus . But Mexican officials said the death toll had risen to 12 . However , more than 150 deaths in Mexico are suspected to have been caused by the virus and are being investigated , officials there said . The higher totals do not necessarily mean that incidence of the disease is increasing , but rather that health investigators are going through their backlog of specimens , said Dr. Keiji Fukuda , assistant director-general of WHO . In addition to Mexico and the United States , the following countries have so far confirmed non-lethal cases : . Austria : 1 Canada : 34 China : 1 Denmark : 1 Germany : 3 Israel : 2 Netherlands : 1 New Zealand : 3 Spain : 13 Switzerland : 1 United Kingdom : 9 . An additional 642 cases are being investigated in the United Kingdom , and Spain has 84 suspected cases . Australia , which has had no confirmed cases , was investigating 114 .
Largest outbreak was in Mexico which had 150 confirmed cases . The virus had spread to 11 countries , with western hemisphere hardest hit . Mexico suspects 11 deaths have been caused by U.S. virus . H1N1 and U.S. the only countries showing human-to-human spread so far .