The number of Americans infected by the AIDS virus each year is much higher than the government has been estimating, US health officials reported, acknowledging that their numbers have understated the level of the epidemic. The United States had roughly 56,300 new HIV infections in 2006 - a dramatic increase from the 40,000 annual estimate used for the last dozen years. The new figure is due to a better blood test and new statistical methods, and not a worsening of the epidemic, officials said. But it likely will refocus US attention from the effect of AIDS overseas to what the disease is doing to this country, said public health researchers and officials. "This is the biggest news for public health and HIV/AIDS that we've had in a while," said Julie Scofield, executive director of the National Alliance of State and Territorial AIDS Directors. Experts in the field, advocates and a former surgeon general called for more aggressive testing and other prevention efforts, noting that spending on preventing HIV has been flat for seven years.