The eggs hatch in your intestine, penetrate the intestinal wall and travel in the blood stream to your liver. From the liver, they travel to the lungs, where you cough up the tiny larvae and re-swallow them. This is how they reach your intestines again, where they attach and mature to the adult stage. Adults grow up to 35 cm long and can shed up to 250,000 eggs a day, which are passed in the feces.

One person may be host to hundreds of these worms, and when the worms are threatened by bodily defenses like fever, or by medications, they can begin to migrate. Migration can cause blockage of the intestines, where they bunch up, or they can try to exit the body from the anus or mouth/nose.