Like many parasitic roundworms, the eggs are excreted in the host's feces. When feces tainted food is eaten by a new host, the eggs hatch and grow in the intestines. The disease is not contagious and cannot be passed from human to human.
Diagnosis is usually from finding the worms in the host's feces or vomit.
Over half a dozen anti-parasitic medications are effective against the worm, but prevention efforts are more important, such as using proper toilet facilities and avoiding tainted food.