Tucked away just south of the right lung lies a disease that’s quietly ravaging the world. Without fanfare, it’s been growing for the last three decades to become what some physicians believe is one of this century’s imminent public health threats. Since it was named in 1980, more than 13,000 articles have appeared in the scientific literature. Just under 500 clinical trials are underway to better understand the disease and find a treatment. It lurks in 20 to 30 percent of adults around the world and 10 to 20 percent of children in the United States. Yet because the disease has few or no symptoms, most don’t know they have it, and it can progress for years undetected. Many find out only when it’s far gone, a few steps away from cancer or organ failure.