Others think the villain might be either cytomegalovirus, a herpes virus, or even the bacteria in dental plaque. But the strongest evidence implicates another bug, called Chlamydia pneumoniae , in heart disease. It is also a close relative of Chlamydia trachomatis , the most common cause of sexually transmitted disease in this country. The idea that bacteria and viruses can damage the heart is not farfetched. The streptococcal bacteria that cause rheumatic fever also attack the heart, causing lingering damage.
Several viruses attack the heart directly, causing myocarditis, which is often fatal.
Staphylococcal and streptococcal bacteria have also recently been shown to cause Kawasaki syndrome, a childhood disease that is marked by severe heart problems. If infectious agents can cause acute heart disease, some researchers reason, it is not a big leap to the idea that they can cause chronic disease as well. Beginning in the late 1980s, researchers such as Dr. J. Thomas Grayston of the University of Washington began finding high levels of antibodies against C. pneumoniae in the blood of patients with heart disease. Few paid much attention to such findings until 1995, when Dr. James Summersgill and his colleagues at the University of Louisville found the same bacterium in the atherosclerotic plaques that blocked blood vessels taken from a patient undergoing bypass surgery. Researchers have since found the bacterium in the blood vessels of virtually every heart disease patient studied, but never in vessels from healthy patients.