The scariest thing about the superbug that killed six people at the National Institutes of Health in Bethesda last year is that such dangerous germs have become so common in U.S. hospitals that doctors viewed the outbreak as routine and saw no need to inform the public. The decision to keep the episode secret until last week has triggered a mild uproar, and deservedly so. A top Maryland health official conceded that the state, which was told of the problem in December, erred by neglecting to notify Montgomery County authorities. People who live or work near the sprawling NIH campus had a right to know that their neighbors at one of the world's most prestigious hospitals struggled desperately for months with an infection immune to antibiotics.