Right now in some areas the southern U.S, a significant percentage of dogs are infected with a potentially life-threatening disease — and many of their owners are likely not even aware.

Canine Chagas disease, which is caused by the parasite Trypanosoma cruzi (or T. cruzi), is estimated to be present in 2% to 6% of dogs in the southern U.S. But in more rural areas, or among working dogs housed in communal kennels or dogs who spend most of their day outside, the rate of infection is closer to 20%, and could be as high as 30% in some parts of the South, according to an expert who spoke with Nexstar.

“Currently, there might be three-quarters of a million, or a million dogs across the U.S., infected,” estimated Rick Tarleton, a regents professor and distinguished research professor at the University of Georgia’s Department of Cellular Biology.