BUENOS AIRES (AFP)--The swine flu deaths of two people in Argentina and a mutation of the H1N1 virus detected in Brazil have added to fears that South America is entering a harsh winter beset by the flu pandemic.

While big pharmaceutical firms are ramping up efforts to mass-produce a vaccine for H1N1, they are still months away from having enough stocks - too late for the Southern Hemisphere's winter flu season.

South America has already recorded five deaths from the disease: two in Chile, one in Colombia last week and, most recently, those of a three-month-old girl and a 28-year-old man with leukemia in Argentina's capital Buenos Aires.

The number of infected cases is outstripping figures put out regularly by the World Health Organization.

According to the latest statistics Tuesday, Chile's confirmed number of patients with H1N1 flu soared by several hundred from 2,355 to 3,125.

Other national health authorities also registered increases with Argentina reporting 733, Peru with 113, Brazil 69, Ecuador 84, Venezuela 44, Uruguay 36, Paraguay 25 and Suriname 13.

Those figures are far overshadowed by the data from North America, the apparent source of the pandemic.

Mexican authorities say they have had 109 deaths and 6,294 infected cases. The U.S. Tuesday added a nine-year-old boy to its death toll, bringing it to 47, alongside 17,855 infected cases. Canada has six deaths and 3,515 infections.

Central America and the Caribbean have also been hit, registering nearly 800 infections and three deaths (one each in Costa Rica, the Dominican Republic and Guatemala).

Although the A(H1N1) virus has been classed as relatively mild since first being detected in April, its unusually strong effect on the young, on those with other underlying health problems, and on the poor have made it a redoubtable challenge.

Some major drug companies have started producing a vaccine for pre-clinical testing, but one of them, Switzerland's Novartis AG (NVS), told the Financial Times it didn't intend to give it away to poor countries.

U.S. rival Baxter (BAX) said Tuesday it should have its H1N1 vaccine commercially available in July.

But there were underlying fears that the virus currently spreading around the world through human-to-human contact might mutate further, possibly into a more deadly form, as happened with the 1918 Spanish flu which killed tens of millions.

Those fears heightened a little Tuesday, when a Brazil's Adolfo Lutz Bacteriological Institute said its researchers had identified and isolated a new strain of the A(H1N1) virus in a Sao Paulo patient.

It wasn't yet known whether that variant, called A/Sao Paulo/1454/H1N1, was more aggressive than the more common type.

The institute said in a statement the mutation comprised of alterations in the hemagglutinin protein which allows the virus to infect new hosts.