According to estimates, about a third of the world's population is infected with the single-celled parasite Toxoplasma gondii, the pathogen of toxoplasmosis. Although harmless for most people, the infection can be dangerous for unborn children and people with weakened immune systems. In these cases, the pathogen can propagate rapidly and destroy infected tissue. It obtains the energy it needs for propagation by tapping the host cell and using its resources.