Researchers at the annual gathering of tropical medicine experts on Tuesday warned of a deadly disease from abroad that is threatening the health of more and more Americans. They weren't talking about Ebola, but Chagas, the "kissing bug" disease.

Called a silent killer because it's often hard to diagnose in the early stages, Chagas is a parasitic infection that can lead to serious cardiac and intestinal complications and even death. It typically spreads through blood-sucking "kissing" bugs that bite on people's faces during the night and is estimated to affect 7 to 8 million people worldwide. The disease can also be spread from blood transfusions, organ transplants and congenital transfer from mother to child, according to the CDC. Until recently it was considered a problem only in Mexico, Central America and South America. Over the past few years, the Centers for Disease Control and Prevention has seen cases across half the United States, but in most cases the victims were believed to have been infected abroad.

As recently as 2012, scientists expressed worry about the "globalization" of Chagas.

Now a team of researchers from Baylor College of Medicine in Houston is challenging that assumption. During a presentation at the American Society of Tropical Medicine and Hygiene meeting in New Orleans, epidemiologist Melissa Nolan Garcia said her team had been following 17 Houston-area residents who had been infected. At least six of them appeared to have been infected locally as they had had insignificant travel outside the United States. Most of the patients spent a lot of time outdoors or lived in rural areas where the bugs are thought to live. The Baylor group also collected 40 kissing bugs near homes in 11 central-southern Texas counties and found that half had fed on human blood as well as that of a dozen kinds of animals ranging from dogs to raccoons.

The researchers analyzed blood donors in Texas between 2008 and 2012 and found that one in every 6,500 donors tested positive for exposure to the parasite -- a figure that is 50 times higher than the Centers for Disease Control estimate.

"We were astonished to not only find such a high rate of individuals testing positive for Chagas in their blood, but also high rates of heart disease that appear to be Chagas-related," Nolan Garcia said in a statement released by the tropical medicine society.

The researchers said that while the number of cases is growing, physicians' awareness of the disease is lagging. When caught in the early stages, the disease can be treated with two drugs, nifurtimox and benznidazole, but if asymptomatic infections are allowed to progress they can lead to serious complications. Many of those who are now recognized as having the disease were flagged after they donated blood and had never been treated for the disease before that.

Virginia was identified by the Baylor researchers as one of the states having a higher number of cases but health officials in the state this summer cautioned that news reports of the disease being prevalent in the area are overstated.

More about Chagas disease: Centers for Disease Control FAQ