White Band Disease (WBD) is a rapidly spreading disease of coral - notably Elkhorn coral (Acropora palmata) and Staghorn coral (A. cervicornis).

It was first noted in the 1970s in the Caribbean, where it has now eradicated around 95% of the two coral species - with severe knock-on effects for other organisms which depend on them. It's also been found in the Red Sea, the Indo-Pacific region, Australia's Great Barrier Reef, and in Indonesia.

White Band Disease (WBD) has caused unprecedented declines in the Caribbean acroporid corals, resulting in their listings as threatened on the US Threatened and Endangered Species List and critically endangered on the IUCN Red List. Yet, despite the importance of WBD, the probable pathogen(s) have not yet been determined.

Source : Sci Rep. 2011; 1: 7.

It's thought very probable that the infective agent is a bacterium, because small-scale experimental studies have found that Tetracycline and Ampicillin - two routinely used antibiotics - can effectively control the disease. This kind of treatment is of course not a viable option over large ocean areas.