A study of 44 grade schools and 10,514 children in the Kansas City bi-state metropolitan area found that 6.6% of the kids showed signs of ringworm, a scalp infection not by a worm but a fungus, most commonly one called Trichophyton tonsurans. Infection causes inflammation and scaling and, in bad cases, permanent hair loss.
The kids were given a general health exam, during which their scalps were sampled by running soft toothbrushes across the head. Then, whatever transferred to the brushes was cultured in the laboratory. (Parental permission was received before this test was done, in case anyone was wondering.)
Published in the journal Pediatrics, the study was undertaken to further knowledge about prevalence of these infections, the authors wrote -- ringworm rates don't seem to be an area of hot investigation. The data do gel with other studies that exist, for example, a 1995 investigation at a single school in Philadelphia, the authors wrote.
Infection rates were especially high among black children, the authors found, at 13%. The scientists are investigating further to see whether a genetic predisposition could be at the root of it.
What is this fungus, anyway? A Web page at a database called Mycology Online has some pictures of what it looks like when grown in culture dishes.
If you're more interested in the medical facts than how you might nurture it in a laboratory, try a December 2009 article on tinea corporis (the technical term for fungal skin infections -- ringworm on the scalp is known as tinea capitis) by dermatologist Dr. Jack L. Lesher Jr. of the Medical College of Georgia.
And here's a September 2009 paper specifically on ringworm of the scalp, by Dr. Grace F. Kao of the University of Maryland School of Medicine and George Washington University Medical School. She notes that rates of ringworm are increasing around the world and goes a little into the history of the condition: "The term tinea originally indicated larvae of insects that fed on clothes and books. Subsequently, it meant parasitic infestation of the skin. By the mid-16th century, the term was used to describe diseases of the hairy scalp. The term ringworm referred to skin diseases that assumed a ring form, including tinea."