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What Causes Scabies?
Scabies is caused by an eight-legged mite (Sarcoptes scabiei var. hominis) that is less than 0.5 mm long. Worldwide, about 300 million people are infected each year. In the U.S., there were outbreaks of scabies in 10 schools in Texas and in hospital workers in Charlotte, N.C., in 2015.
What Are Risk Factors for Scabies?
The highest risk factor for scabies is skin contact with a person with scabies. Transmission of the infection during sex is very common. Also included is physical contact (nonsexual) with an infected person or items that have been in contact with the skin of an infected person (for example, clothing, towels, bedding, or even items like chairs or couches). These nonsexual contacts are how one person may infect other family members, such as a baby or child. However, people with STDs are at risk to become infected and then harm the health of others by both sexual and nonsexual transfer of the mite.
Nonsexual outbreaks can occur. For example, an outbreak occurred in an El Paso, Texas, child care facility and three health care facilities in Dayton, Ohio, in 2017.
What Is the Life Cycle of the Scabies Mite?
The life cycle of the scabies mite starts when the female tunnels (burrows) into the skin and deposits her eggs. Larvae hatch from the eggs within three to 10 days and molt to become nymphs. Nymphs mature into adults that deposit additional eggs and live approximately four weeks. Burrowing and movement of the mites cause intense itching due to a type of allergic reaction to mite proteins. If the person has never been exposed to scabies before, he or she may not show symptoms until four to six weeks after the initial infestation. Individuals who have been exposed in the past usually show symptoms within a few days.
Last Reviewed 8/30/2017
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