Ascaris lumbricoides is among the most common parasitic diseases in the world, and the CDC estimates approximately 1 billion cases worldwide. Ascaris lumbricoides in uncommon now in the United States, but worldwide the disease burden is very high. Fortunately many infected persons have no symptoms, and if symptoms are noted they are often mild, for example abdominal cramping. In cases where there is a heavier infestation with the worms they may migrate outside the abdomen causing lung symptoms including cough, or can cause intestinal blockage. In children poor growth or nutritional deficiency due to heavy worm burden is common.
Ascaris lumbricoides, along with hookworm and whipworm, is considered a soil-transmitted helminth, as the primary means of infection is the ingestion of soil contaminated by the eggs that are passed in the feces of humans infected with the worms. In communities where defecation outdoors, especially near crops, or where human waste is used as fertilizer high rates of soil-transmitted helminthes like Ascaris lumbricoides are often encountered.