Visiting medical specialists in American Samoa are warning parents to be vigilant about seeking health care for their children's sore throats in an attempt to prevent heart disease.
A cardiologist Dr Laurie Armsby says strep throat is a big problem in American Samoa and is the main cause of rheumatic fever which can lead to damaged heart valves.
A team from Oregon Science and Health University screened nearly 200 children this month and found 30 who they believe had silent rheumatic fever affecting their hearts.
Dr Armsby says treatment with antibiotics can stop strep throat from causing permanent heart damage.
"There's different kinds of strep and we don't actually know; we think that there's a virulent, really virulent, aggressive form of strep on this island and in parts of the world, that causes rheumatic heart disease from strep throat. But we also think that there may be something within the population that makes them more vulnerable to it."
Dr Laurie Armsby.
LBJ Hospital's Paediatrics team says 180 children in American Samoa under the age of 17 have a history of rheumatic fever and 65 percent of them have signs of rheumatic heart disease.