(I) Parasitic infections are common in rural Africa, Asia and South America. (II) However, they are rare in developed countries. (III) But people from developed countries who visit developing countries can very easily be infected by parasites. (IV) Those parasites that infect the intestine may stay there or may burrow through the intestinal wall and infect other organs. (V) So, unknowingly, they return home with the infection, which may not be readily diagnosed, because it is so uncommon.