The speed at which Indonesia has become the country with the most human bird-flu deaths has experts worried, but they say the pace will continue until the problem is tackled at the source. The country's 43 reported deaths in just over a year comes as the H5N1 virus spreads virtually unchecked among the billions of poultry in backyard farms throughout the vast archipelago. Indonesia became the nation hardest hit by bird flu after local tests concluded a 16-year-old boy from Jakarta's outskirts succumbed to the H5N1 virus late Monday.