Turtles from the heavily polluted Indian River Lagoon (IRL) had compromised immune function. Those with tumors (Green Turtle Fibropapillomatosis or GTF) had less immune competence. Habitat quality, disease state, and immune function are intertwined. Polluted environments impact the immune system and make animals more prone to the expression of GTF, which in turn further compromises the immune system. This vicious cycle may explain why some areas have such a high incidence of GTF, while other areas have turtles that test positive for the GTF virus, but are clinically healthy.