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Disease History, Characteristics, and Transmission

Scope and Distribution

Treatment and Prevention

Impacts and Issues



Yaws is a chronic infection, which primarily affects the skin, bones, and cartilage of its victims. Yaws is nearly unknown in developed countries. A spiral shaped bacterium called Treponema pertenue causes yaws. These bacteria, called spirochetes, are closely related to the bacteria that causes syphilis. The spirochetes spread from person to person by direct contact of skin with infectious yaws sores. Crowding, poor sanitation, and dirty water all contribute to spreading yaws, and the disease primarily affects the poor in tropical areas of Africa, Asia, and Latin America.

Disease History, Characteristics, and Transmission

The initial lesion of yaws appears where the bacteria enter the skin, and soon a red bump called a papule develops. The papule, measuring 0.8–2 in (2–5 cm) in diameter, is painless but often itchy. Scratching results in an open, ulcerated sore. This first sore takes three to six months to heal, and meanwhile, the spirochetes spread to other parts of the body through the lymph system or the blood stream.

Soon more red papules similar to the initial sore develop and eventually, the infected individual has multiple sores spread over the body. During the wet season in the tropics, these sores may get quite large resembling fleshy red wartlike growths. They eventually heal, but often scars develop at the sites of the sores. The disease is not fatal, but relapses are common up to 10 years after the initial infection.

Other problems caused by the yaws bacteria include enlarged lymph nodes in the armpits, neck, or groin. Sores may develop on the feet (making walking quite difficult) or the palms. The bones, particularly the bones of the fingers and the long bones in the arms and legs, may be affected, as well as the skin. Pain from the affected bones makes sleeping difficult.

The disease may seem to go away after a few years, but the bacteria are alive and well in the skin and bones. The latent (dormant) period may persist, but in about 10% of those afflicted, the sores reappear after 5–10 years. When yaws reappears, the individual suffers marked thickening of the skin on the palms and soles as well as hard nodules under the skin around the joints. Particularly disfiguring are bony growths in the bone of the upper jaw and nose. The skin and membranes of the nose and upper mouth can be involved, and result in the destruction of the upper mouth and nasal passages. Where the mouth and nose were, a gaping hole develops.


INCIDENCE: The number of new cases of a disease or injury that occur in a population during a specified period of time.

LATENT INFECTION: An infection already established in the body but not yet causing symptoms, or having ceased to cause symptoms after an active period, is a latent infection.

PAPULE: A papule is a small, solid bump on the skin.

RE-EMERGING INFECTIOUS DISEASE: Re-emerging infectious diseases are illnesses such as malaria, diphtheria, tuberculosis, and polio that were once nearly absent from the world but are starting to cause greater numbers of infections once again. These illnesses are reappearing for many reasons. Malaria and other mosquito-borne illnesses increase when mosquito-control measures decrease. Other diseases are spreading because people have stopped being vaccinated, as happened with diphtheria after the collapse of the Soviet Union. A few diseases are reemerging because drugs to treat them have become less available or drug-resistant strains have developed.

Scope and Distribution

Yaws occurs mostly in children under age 15, and mostly in tropical areas of Africa, Asia, and Latin America. The World Health Organization estimates that up to 500,000 people have yaws in either its latent or active form.

Treatment and Prevention

Yaws is a disease with a cure. At a cost of about 32 (U.S.) cents, a single injection of long-acting penicillin given in the muscle rapidly destroys the yaws bacteria. Relapses after treatment appear to be rare, and yaws bacteria have not become resistant to penicillin. For those with penicillin allergies, tetracycline or erythromycin is the drug of choice.

Impacts and Issues

Children are most often afflicted, yet current pediatric textbooks devote less than a page to the description and treatment of yaws. Children need not suffer the disability and disfigurement of yaws, and eliminating yaws from the globe is a possibility. Yaws can be defeated because it only occurs in humans and only occurs in specific areas making surveillance efforts easier. Additionally, an inexpensive drug cures yaws. In the 1950s, the World Health Organization mounted a campaign to eliminate yaws, and after more than 300 million people received treatment, the global incidence of yaws dropped more than 95 percent. Unfortunately, interest waned, and with reduced surveillance, yaws has made a comeback, reemerging in the twenty-first century.

In early 2007, the World Health Organization convened a meeting to revive interest in eliminating yaws. The strategy developed at the meeting involves identifying the people at risk for yaws, actively treating all infected people and their close contacts, and most importantly a renewed surveillance effort. Participants in the meeting announced the goal of eliminating yaws in South-East Asia by 2012.

Archeologists found evidence of yaws in the bones of human ancient ancestors. Modern medicine has the ability to ensure this disease disappears from the historical record, and no more children suffer the disfigurement of yaws.

See AlsoRe-emerging Infectious Diseases.


Web Sites

World Health Organization. “Yaws.” <http://www.searo.who.int/en/Section10/Section2134.htm> (accessed May 2, 2007).

World Health Organization. “Yaws Elimination in India: A Step Towards Eradication.” <http://www.whoindia.org/EN/Section210/Section424.htm> (accessed May 2, 2007).

L. S. Clements

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Yaws is a chronic illness which first affects the skin, and then affects the bones.


Yaws tends to strike children, particularly between the ages of two and five. It is common in areas where poverty and overcrowding interfere with good hygiene practices. The most common locations are in rural areas throughout Africa, Southeast Asia, and in locations bordering the equator in the Americas.

Causes and symptoms

Yaws is caused by a spiral-shaped bacterium (spirochete) called Treponema pertenue. This bacterium belongs to the same family as the bacterium that causes syphilis.

Yaws is passed among people by direct skin contact. It requires some kind of a scratched or insect bitten area in order for the bacteria to actually settle in and cause infection. An injured spot on the leg is the most common part of the body through which the bacteria enter. Young children, who are constantly bumping themselves in play, who wear little clothing, who do not wash their hands often, and who may frequently put their hands in their mouths, are particularly susceptible.

The first symptom of yaws occurs three to four weeks after acquiring the bacteria. The area where the bacteria originally entered the skin becomes a noticeable bump (papule). The papule grows larger and develops a punched-out center (ulcer), covered with a yellow crust. Lymph nodes in the area may become swollen and tender. This first papule may take as long as six months to heal. Secondary soft, gummy growths then appear on the face, arms and legs, and buttocks. These soft, tumor-like masses may grow on the soles of the feet, causing the patient to walk in an odd and characteristic fashion on the sides of his or her feet (nicknamed "crab yaws"). More destructive tumors may then disrupt the bones of the face, the jaw, and the lower leg. Ulcers around the nose and on the face may be very mutilating.


Samples taken from the first papules may be examined using a technique called dark-field microscopy. This often allows the spirochetes to be identified. They may also be identified in fluid withdrawn from swollen lymph nodes. Various tests can also be run on blood samples to determine if an individual is producing antibodies (special immune cells) which are specifically made in response to the presence of these spirochetes.


A single penicillin injection in a muscle is sufficient to completely end the disease.


Without treatment, yaws is a terribly disfiguring chronic illness. With appropriate treatment, the progression of the disease can be completely halted.


For a time, the World Health Organization (WHO) was working to totally eradicate yaws, just as smallpox was successfully eradicated. This has not occurred, however. WHO continues to work to identify and respond to outbreaks quickly, in an effort to at least slow the spread of yaws.



Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. (800) 311-3435, (404) 639-3311. http://www.cdc.gov.


Papule A raised bump on the skin.

Ulcer A punched-out, irritated pit on the skin.

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yaws / yôz/ • pl. n. [treated as sing.] a contagious disease of tropical countries, caused by a bacterium (Treponema pallidum subsp. pertenue) that enters skin abrasions and gives rise to small crusted lesions that may develop into deep ulcers.

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yaws (framboesia) Contagious skin disease found in the humid tropics. It is caused by a spirochete (Treponema pertenue), related to the organism causing syphilis. Yaws, however, is not a sexually transmitted disease (STD), but is transmitted by flies and by direct skin contact with the sores. It may go on to cause disfiguring bone lesions.

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yaws (pian, framboesia) (yawz) n. a tropical infectious disease caused by the presence of the spirochaete Treponema pertenue in the skin and its underlying tissues. Yaws occurs chiefly in conditions of poor hygiene. It is characterized by small tumours, each covered by a yellow crust of dried serum, on the hands, face, legs, and feet. These tumours may deteriorate into deep ulcers. The disease responds well to treatment with antibiotics.

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yawsapplause, Azores, cause, clause, Dors, drawers, gauze, hawse, indoors, Laws, outdoors, pause, plus-fours, quatorze, Santa Claus, taws, tawse, yaws, yours •menopause

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yaws contagious skin-disease of tropical countries. XVI. of unkn. orig.

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