The H1N1 pandemic that swept across the United States and other parts of the world last year was found to be no more serious than most other seasonal strains of the disease, a new study has found.

The U.S. centers for Disease Control and Prevention suggested that there were between 43 million to 89 million cases of swine flu in the United States between April 2009 to April 2010 of which 274,000 had to be hospitalized and 12,470 lost their lives.

Researchers at the Marshfield Clinic Research Foundation in Wisconsin said the pandemic H1N1 virus had disproportionately affected children and younger adults but the symptoms were almost similar to the seasonal influenza viruses that come back year after year.

In fact, children, young adults, pregnant women and people with underlying chronic medical conditions had a higher risk of hospital admission and serious complications when infected with the pandemic virus, said lead researcher Dr. Edward A. Belonga.

However, the researchers said they had not done enough studies to determine whether the pandemic flu was deadlier or caused more critical ailments than the normal influenza strains.

The study, published in the latest issue of the Journal of American Medical Association, said one implication of the study was that the higher incidence of death or serious illness from the H1N1 pandemic in other studies could have been due to a high level of transmission among children and young adults than any additional virulence.

The researchers compared the H1N1 pandemic flu with seasonal flu as well as the H3N2 strain of the flu. Of the 6,800 people who volunteered for the study, the researchers found 545 had the H1N1 pandemic while 221 suffered from the seasonal strain and 632 patients had contacted the H3N2 flu. Most of these patients were aged between 10 and 25.

Hospital records showed that among children, the H1N1 were not linked to hospitalization or pneumonia compared with both the seasonal strain of the virus and the H3N2 flu. Among adults, four percent of those with the H1N1 pandemic were hospitalized as were 2.3 percent of those who caught the seasonal virus and 1.1 percent of those with H3N2 flu.