At least 1 million Americans have contracted the novel H1N1 influenza, according to mathematical models prepared by the Centers for Disease Control and Prevention. Data from the field indicate that the virus is continuing to spread even though the normal flu season is over and that an increasing proportion of victims are being hospitalized.

Meanwhile, the virus is continuing to spread through the Southern Hemisphere, infecting increasing numbers of people and at least one pig.

Nearly 28,000 laboratory-confirmed U.S. cases of the virus, also known as swine flu, have been reported to the CDC, almost half of the more than 56,000 cases reported to the World Health Organization.

But Lyn Finelli, a flu surveillance official with CDC, told a vaccine advisory committee meeting in Atlanta on Thursday that standard models of viral spread indicate that many times that number have been infected.

Although 1 million seems like a high number, between 15 million and 60 million people in the United States are infected by influenza virus during a normal flu season.