Pinworm infection in humans occurs when oral contact with infected fecal matter occurs, according to the Centers for Disease Control and Prevention. This transfer can happen when a hand touches fecal matter or when contact happens with a contaminated item such as bedding or clothing.
Pinworms are tiny parasitic worms measuring about 0.5 inches long, according to WebMD. They look like tiny white threads and lay eggs so small they can't be seen with the naked eye. Those eggs may get on the hands or under fingernails without being seen, leading to infection. The worms live in a human's intestines. Female pinworms lay their eggs around the anus, usually at night, causing itching in that area. A child who scratches the area unknowingly scrapes off the eggs. Those eggs then get on other items the child touches, spreading the eggs to others. The eggs can survive for two to three weeks outside of a human host.
Pinworms are most common in children, but adults can become infected as well. The eggs spread easily in locations with lots of children such as schools or day care centers. The parasites also tend to spread easily in the home of an infected person. Once diagnosed, a pinworm infection is treated with medication. Other household members and caretakers should also receive treatment, the CDC advises. Proper hygiene is also important to prevent re-infection.