MANILA, PHILIPPINES — Leptospirosis is one of the Philippines’ most persistent and least talked-about health threats: a bacterial disease carried in contaminated water and soil, spiking every year the moment the rains and the floodwaters come. Two new peer-reviewed studies out of the University of the Philippines Diliman and the Philippine Genome Center now show that the picture may be worse than health workers assumed, not because the bacterium is new, but because of where scientists just found it living, and how completely it has settled in.