Ask the average American about chlamydia, and you will probably evoke an uneasy cringe. Most people think immediately of one of the world's most common sexually transmitted diseases (STDs). But the term actually refers to an entire genus of tiny bacteria that can ignite a variety of serious illnesses.
Ask a poor mother in Africa about chlamydia, and she may tell you that flies transmitting this infection gave her two young children the painful eye condition known as conjunctivitis. This illness--caused by a strain of Chlamydia trachomatis (the species that also causes STDs)--can lead to trachoma, a potentially blinding disease. In industrial countries, an airborne species, C. pneumoniae, causes colds, bronchitis and about 10 percent of pneumonias acquired outside of hospitals. Researchers have even drawn tentative links between C. pneumoniae and atherosclerosis, the artery-narrowing condition that leads to heart attacks and strokes.