The whole process - from egg ingestion to egg deposits - takes about two or three months. The fertilized eggs must be in soil for at least two to four weeks before they become infective. Female worms can produce 200,000 eggs a day if there are both female and male worms in the intestines, and the eggs leave your body in feces. Female worms can be more than 15 inches (40 centimeters) long and a little less than a quarter inch (6 millimeters) in diameter. Once they're back in the intestines, the parasites grow into male or female worms. After maturing for about 10 to 14 days in your lungs, the larvae break into your airway and travel up the throat, where they're coughed up and swallowed.

Larvae hatch from the eggs in your small intestine and then go through the intestinal wall to travel to the heart and lungs via the bloodstream or lymphatic system. People can accidentally ingest (swallow) contaminated soil through hand-to-mouth contact or by eating uncooked fruits or vegetables that have been grown in contaminated soil. The tiny (microscopic) ascariasis eggs can't become infective without coming into contact with soil.

Flat heaf worms