In 2002, Kathryn P Sutherland an associate professor of biology at Rollins College, Florida and her colleagues discovered that the bacterium killing elkhorn coral was the same as bacterium found in the human body; identifying Serratia marcescens as the cause of white pox.
Once identifying the bacteria, the research team went onto discover the source of it. After analyzing samples from Key deer, seagulls and other native species, they realized that the strain of Serratia marcescens found in white-poxed elkhorn corals was specific to humans. Meaning that the main source of disease plaguing the Florida Keys coral reef ecosystem is human sewage.
After exposing elkhorn corals in isolated tanks to Serratia marcescens, in just 5 days the bacterium would cause the coral to disease. Scary considering most the the Florida Keys economy is based off of water-related activities. One scientist, James W. Porter speaks of the serious impact of the situation, "we are killing the goose that lays the golden egg."
This research has revealed a new transmission of disease, previously unknown to humans. It is well documented that disease can move from animals to humans - rabies, bird flu, HIV - but documentation on human-to-wildlife diseases are recent and rare. This is the first time ever scientists have seen a human disease has caused population declines of marine vertebrate.
The upside of this problem is that it's curable. With proper water treatment, and advancing technologies in the field, corals will be less likely to become susceptible to human disease. The entire Florida Keys are going through a local upgrade of their water treatment.