juvenile stage 1 is known as 'rhabditiform'. The rhabditiform larvae grow and molt in the soil, transforming into a juvenile stage 2. The juvenile stage 2 molts once more until reaching the juvenile 3 stage, which is also called 'filariform'; this is also the infective form. The transformation from rhabditiform to the filariform usually takes 5–10 days. This larval form is able to penetrate human skin, travel through the blood vessels and heart, and reach the lungs. Once there, it burrows through the pulmonary alveoli and travels up the trachea, where it is swallowed and carried to the small intestine. There, it attaches to the intestinal wall, and matures into an adult and begins reproduction. Adults live in the lumen of the intestinal wall, where they cause blood loss to the host. The eggs produced by the adults end up on the soil after leaving the body through the feces; female hookworms produce up to 30,000 eggs per day. On average, most adult worms are eliminated in 1–2 years. The N. americanus lifecycle only differs slightly from that of A. duodenale. N. americanus has no development arrest in immune hosts and it must migrate through the lungs. Pathogenesis and symptoms The pathology of N. americanus is divided into two stages – larvae and adults. The larvae penetrate the uninfected skin and travel through various organs, including the respiratory tract and lymph nodes. Once in the lymph nodes, the larvae start entering the blood, lungs, and intestines. Some larvae cannot readily enter the dermis and remain trapped in the skin, causing skin irritation and cutaneous larva migrans. Other symptoms include excessive coughing and dyspnea (short of breath) during larval migration. Once attached to the intestinal wall, N. americanus resides and matures into adults, penetrates blood vessels, and sucks blood. The incubation process of the larvae begins once entered into the small intestine; therefore, symptoms may not arise for up to 40 days, but this is variable from person to person. Blood loss from sites of intestinal attachment may cause iron-deficiency anemia and protein loss. One individual N. americanus can cause 30 μl of blood loss per day. Iron-deficiency anemia can cause intellectual disability and growth insufficiency in children. Further, infected patients experience abdominal pain (exacerbated by meals) with diarrhea, bloating, and nausea. Epidemiology In the United States, 95% of human hookworm cases are caused by N. americanus, primarily in young school