Keeping tabs on the HIV/AIDS epidemic is crucial for formulating treatment and prevention strategies, but the U.S. has greatly underestimated the annual number of new infections. An assay that differentiates between recent and long-standing infections has led scientists to conclude that 56,300 individuals in the U.S. contracted the virus in 2006; previous annual estimates had it at 40,000. African-Americans (83.7 infections per 100,000) and Hispanics (29.3 per 100,000) continue to be disproportionately affected compared with whites (11.5 per 100,000). The results, in the August 6 Journal of the American Medical Association, follow disappointing news about HIV vaccines, including the cancellation of a large trial called PAVE 100.