Individuals become infected, usually by walking bare footed across contaminated soil.  Soil contamination can be extremely heavy, particularly in those cultures which utilize human excreta as fertilizer.  The eggs are susceptible to urine, however, and it has been found that if fecal material is mixed with urine the eggs can be killed. There are three pathological phases to hookworm infections:

Cutaneous or invasive phase: When larvae initially penetrate the skin they can cause irritation and itching and if they fail to locate a blood capillary they can wander through the skin causing a condition known as cutaneous larval migrans, leaving a track visualized under the skin by the presence of the host inflammatory reaction.

Pulmonary phase: This occurs during the period when the larvae are bursting out of the capillaries in the lungs into the alveolar spaces.  This causes local hemorrhaging at the site.  This is rarely symptomatic, except when there is a heavy infection, when it can result in pneumonitis, and can also cause a cough and a sore throat.

Intestinal phase: Adult worms are usually restricted to the anterior third of the small intestine, but where infections are very heavy they can occupy the whole length of the small intestine.  The worms clamp onto the mucosa abrading the surface and sucking the blood.  Proteolytic enzymes from the dorsal pharyngeal gland are released into the buccal cavity which aid in digestion.