Of the different types of flu virus, influenza A poses the greatest threat to human health and at any point in time, about 5-15% of the world's entire population are infected with these strains. Together, they kill up to half a million people every year and the death toll rises sharply when pandemics sweep the globe.
Today, two papers published in Nature and Science shed new light on the origins of these epidemics. By prying into the private lives of flu viruses, the studies provide fresh clues about the birthplaces of new strains, their flight plans around the world and the locations of possible 'viral graveyards'.
