It is found in association with poor personal hygiene, poor sanitation, or where human feces are used as fertilizer.
Infection occurs when food or drink contaminated with roundworm eggs is ingested.
The eggs hatch releasing larvae within the intestine. The larvae then migrate through the blood stream to the lungs, exit through the bronchial tree and are swallowed. Once back in the gut they mature into adult roundworms. Adult worms live in the intestine where they lay eggs that are expelled with the feces. It is estimated that 1 billion people are infected worldwide.