Health officials have said the true number of swine flu cases globally was underestimated.
Although most cases appear to be mild, just as in seasonal flu, the swine flu strain has killed, with 48 confirmed deaths in Mexico, two in the United States, one in Canada and one in Costa Rica.
Australia has reported its first case after a woman tested positive for the disease as she returned from a trip to the US.
Health officials said the influenza season is just beginning there, and the A(H1N1) strain could mix with circulating seasonal flu viruses or the H5N1 avian influenza virus to create new strains.
The Centres for Disease Control has reported 2,254 confirmed US cases of the virus with 104 people in the hospital, up from 1,639 cases previously.
Japan reported four cases, and globally officials reported more than 4,200 people in 30 countries had been ill.
Mexican health ministry spokesman Carlos Olmos said the government was testing thousands of samples to confirm which patients with severe respiratory symptoms were actually infected with the flu.
He said more than 5,000 tests had been done on suspected cases and that 1,578 people were ill but were being treated.
Meanwhile, eight new cases of swine flu in England and another case in Scotland were confirmed today by health officials.
Three adults and six children are affected, bringing the total in the UK to 48.
The first two cases of swine flu were confirmed in Norway with both people recovering from 'mild' forms of the disease.
Both are students in their 20s who have recently spent time in Mexico.
Health officials in Panama City confirmed that country's first two cases of swine flu.
Italy reported its first case of swine flu contracted inside the country by a person who had not travelled to Mexico or the US.
The health ministry in Rome said the man's grandson had recently been to Mexico.
And Brazil confirmed its first case of swine flu transmitted from person to person, taking the number of confirmed cases in Latin America's largest nation to six.
Meanwhile, officials said British scientists had produced the first genetic fingerprint of the swine flu virus in Europe, following a similar breakthrough in north America.
