The very simple life cycle of E. vermicularis ensures a high human prevalence. Tiny eggs deposited around the anus by a female worm spread the infection. Each female worm can produce more than 10,000 eggs during her lifespan. When someone with pinworms scratches their perianal area, eggs may lodge under their fingernails and be spread to anything he or she touches. Infested dust, clothing, bedding, or toys can also spread eggs. When someone else accidentally ingests these eggs, they also become infected.