is the most common human worm infection
. Infection occurs worldwide and is most common in tropical and subtropical areas where sanitation and hygiene are poor. Children are infected more often than adults. In the United States, infection is rare, but most common in rural areas of the southeast. Anesthesia
appears to agitate the worms and when there is infection of adults in the lungs they can exit the mouth and nose. The normal life cycle of ascaris is to migrate to the lungs for the larval stage and grow to an adult in the intestines, but sometimes the adults reside in the lungs. Ascaris eggs are found in human feces. After feces contaminates the soil, the eggs become infectious after a few weeks. Infection occurs when a person accidentally ingests infectious Ascaris eggs. Once in the stomach, immature worms hatch from the eggs. The larvae are carried through the lungs and then to the throat where they are swallowed. Once swallowed, they reach the intestines and develop into adult worms. Adult female worms lay eggs that are then passed in feces; this cycle takes between 2-3 months.