U.S. health officials said last week that as many as 1 million Americans have been infected with the H1N1 flu virus. At a press briefing Friday, the Centers for Disease Control's Dr. Anne Schuchat said the CDC had received reports of over 6,000 new U.S. cases in the past week, more than in any other week since the outbreak began in April. "The key point is that this new infectious disease is not going away," Schuchat told reporters. More than 27,000 confirmed U.S. cases have been reported to the CDC, including 3,000 hospitalizations and 127 deaths. "Those reported cases are really just the tip of the iceberg," Schuchat said, noting that models of viral spread indicate many times that number have been infected. Several drugmakers are now working on a vaccine to protect against the new virus.