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Symbol for the element yttrium.


(yard) A measure of 3 ft or 36 in.; equal to 0.9144 m.


(yar′ō) Any of approx. 100 species of perennial herbs of the genus Achillea, esp. A. millefolium. A. millefolium contains salicylic acid, asparagine, sterols, flavonoids, and tannin. It has been used as a diaphoretic, astringent, tonic, and stimulant. SYN: common yarrow.


(yan) To open the mouth involuntarily and take a deep breath, a movement mediated by neurotransmitters in the hypothalamus. It is often accompanied with stretching. and is associated with drowsiness, boredom, anxiety, or fatigue. yawning (yan′ing), n.


(yaz) [From Carib yaya, sore] A chronic, infectious tropical disease that affects skin, bones, and joints.

 INCIDENCE: It is a common illness in school-aged children in tropical, resource-poor countries.

 CAUSES: Yaws is caused by a spirochete, Treponema pallidum subspecies pertenue, a member of the same species of spirochetes that causes syphilis. The disease is spread by person-to-person contact when an infected lesion on the skin of one individual (or the clothing worn by that person) rubs against the skin of another. Despite its relationship with syphilis, the disease is not sexually transmitted.

 SYMPTOMS AND SIGNS: During the initial phase of infection with yaws a large, painless, warty papule that resembles a strawberry forms on the skin at the inoculation site. This lesion (the “mother yaw”) heals, but after about a month of dissemination of treponema through blood vessels, multiple lesions appear elsewhere on the body, esp. near the mouth, nose, anus, and other mucus membranes. After these lesions heal, the disease may be quiescent for several years until it becomes clinically apparent again because of the destructive changes the infection has on cartilage, bones (osteoperiosititis) and, sometimes, other organs. Thickened lesions form on the soles of the feet. These may crack or ulcerate making it painful for patients to walk. Disfiguring oral and nasal deformities occur in some patients. The chronic deformities caused by yaws do not consistently resolve even after antibiotic therapy.

 DIAGNOSIS: Darkfield microscopy of exudate swabbed from the skin is used to identify the spiral-shaped bacteria that cause yaws. Serological tests for syphilis are positive in patients with yaws (including the rapid plasma reagin RPR and VDRL tests).

 PREVENTION: International campaigns to eliminate the disease from African, Pacific, and South American countries were carried out in the mid-twentieth century and markedly reduced the incidence and prevalence of yaws. Some countries, including India, have eradicated the disease entirely through population-based treatment campaigns. Infectious disease experts recommend treating every child in a hyperendemic area to eradicate the disease.


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