Strongyloides is a genus containing some 50 species of obligate gastrointestinal parasites of vertebrates. Strongyloides stercoralis is the scientific name of a human parasitic roundworm causing the disease of strongyloidiasis. The Strongyloides stercoralis nematode can parasitize humans. The adult parasitic stage lives in tunnels in the mucosa of the small intestine. S. stercoralis can be found in areas with tropical and subtropical climates but cases also occur in temperate area, more frequently in rural areas. S. stercoralis has a very low prevalence in societies where fecal contamination of soil or water is rare. Many people infected are usually asymptomatic at first. Symptoms include dermatitis: swelling, itching, larva currens, and mild hemorrhage at the site where the skin has been penetrated. If the parasite reaches the lungs, the chest may feel as if it is burning, and wheezing and coughing may result, along with pneumonia-like symptoms (Löffler's syndrome). The intestines could eventually be invaded, leading to burning pain, tissue damage, sepsis, and ulcers. In severe cases, edema may result in obstruction of the intestinal tract, as well as loss of peristaltic contractions. Strongyloides infection in immunocompromised individuals (particularly following the administration of steroids, for example following transplant surgery) can result in disseminated strongyloidiasis, in which worms move beyond the confines of the gut into other organs.