THURSDAY, Feb. 26 (HealthDay News) -- The best way to prevent the developing world incidence of rheumatic fever and the heart disease it can cause is through accurate diagnosis and thorough treatment of strep throat, according to an American Heart Association scientific statement.

While generally rare in the United States, rheumatic fever and subsequent rheumatic heart disease is the leading cause of cardiovascular death in people under age 50 in developing nations. The inflammatory disease, which can affect connective tissues in the skin, joints and brain, and possibly cause irreversible heart damage, briefly resurfaced in localized U.S. civilian and military populations in the 1980s.

"This reappearance of acute rheumatic fever reminds physicians, parents and others about the importance of continued attention to prevention of rheumatic fever in the United States and in other developed countries," Dr. Michael A. Gerber, lead author of the scientific statement, said in a heart association news release.

The statement, published in Circulation, updates one issued 14 years ago and cites swabbing the back of the throat to obtain a culture and good clinical judgment as the best ways to diagnose strep throat.

One particular strain of strep throat, known as group A a-hemolytic streptococcus, or GAS pharyngitis, can develop into rheumatic fever if not properly treated with antibiotics.

"It's important to know that, while strep throat is most common in children five to 15 years old, most sore throats in this age group are not caused by this particular type of strep," said Gerber, a professor of pediatrics in the division of infectious diseases at Cincinnati Children's Hospital Medical Center in Ohio. "In fact, most are caused by viruses, which do not raise the risk of rheumatic fever and are not treatable with antibiotics."

Symptoms of GAS pharyngitis may include sudden-onset of sore throat, pain when swallowing, and fever above 101 degrees. In children, headache, stomach pain, nausea and vomiting are also possible. The infection can occur with other upper respiratory tract infections, so an accurate throat culture is important for proper diagnosis and treatment.

If the infection progresses to rheumatic fever, the symptoms may include: fever; sore, tender or red swollen joints; pain that travels from one joint to another; heart palpitations; chest pain; shortness of breath; skin rashes; and small but painless bumps under the skin.

Even those who are properly treated with antibiotics after an initial bout of rheumatic fever are not safe. The chances of a recurrence are high if they again develop strep throat, and continuous treatments with penicillin or similar antibiotics are necessary to prevent further recurrences. Otherwise, the fever can worsen rheumatic heart disease or cause it in those who escaped it the first time.