Lethal infections are killing off populations of creatures ranging from vultures to kangaroos, from coral to honeybees and from amphibians to reptiles. More than pollution, diseases spread by humans are today the biggest threat to a variety of species. For long, ecologists, biologists and governments ignored the threat that emerging diseases pose to natural ecosystems. Conservationists believe that enacting laws will not be enough. There has to be a better understanding of how diseases are spread through wild populations and which ones exist there naturally, and how environmental changes, such as crowding within dwindling habitats, can speed contagion.