The total death tally of swine flu has risen to 549 as the global number of the new flu infection cases surpassed 113,000 people, Russia's chief sanitary doctor said on Tuesday, according to the Russian leading newspaper RIA Novosti report.

According to data from all sources, 113,507 cases have been reported across the globe, including 549 deaths, Gennady Onishchenko said.

The World Health Organization (WHO) didn't update the number of swine flu cases, but in its recent report on July 6 confirmed 94,512 officially registered cases and 429 deaths in 135 countries and territories worldwide.

Japanese scientists have released a report Tuesday saying people who were born before the 1918 flu pandemic seem to have immunity to the current swine flu, but not to the seasonal flu.

The 1918 influenza pandemic killed up to 100 million people worldwide. Those who survived the pandemic have antibodies against swine flu, or the A/H1N1 virus, the research said.

“I’m very concerned because clearly the (swine flu) virus is different from seasonal influenza,” said study leader Yoshishiro Kawaoka. “It’s a lot more severe.” But it is still not as severe as the 1918 influenza, he said.