In all cases, tungiasis by itself only caused morbidity, though secondary infection may lead to mortality. The life cycle section presents the Fortaleza stages from the flea's developmental perspective. The discussion is specific to symptoms of human infection. The clinical presentation in humans follows the Fortaleza Classification as the stage of infection will determine the symptoms present. The following discussion will give an overview of the symptoms beginning in stage 2 because patients are not likely to present themselves at the early stages of infection, mostly because the flea's burrowing is usually not felt. This may be due to a keratolytic enzyme secreted during stage 1.