Winter is flu season in the world's temperate regions, but scientists still aren't sure why. Now, it turns out that the answer may have been staring them in the face all along. A reanalysis of data from past studies suggests that low absolute humidity--not low relative humidity, the factor many scientists have studied--helps the virus survive and the flu spread. Explanations abound for why flu is king in winter, only to disappear come summer. Researchers have suggested that the virus might survive better in colder temperatures, that people are more exposed when huddled indoors, and that lower melatonin and vitamin-D...