For decades, doctors have made a curious observation: people stricken with a particular heart or blood infection often developed colorectal cancer.
The infectious agent? A bacterial species called Streptococcus gallolyticus, known as Sg, somehow liberated from its home in the gut. So tight was this association (up to a 60 percent chance of also having colon cancer), that it became de rigueur to check lower GI tracts for signs of cancer when a person was diagnosed with an Sg heart or blood infection.
