Over the past couple of decades, various coral diseases have been recorded in various parts of the world. Coral diseases were first recognised in the Caribbean, but have now been recorded throughout the Indo-Pacific (Antonius 1995), including, more recently, the Great Barrier Reef (Wachenfeld et al. 1998; Baird 2000). For example, a newly described coral disease on Indo-Pacific reefs is caused by Halofolliculina corallasia, a coral-killing ciliate (Antonius 1999a). The disease damages the skeleton and it is found on a wide variety of massive and branching corals and is somewhat similar to Black Band Disease. This disease was found on reefs of the Sinai (Red Sea), Mauritius (Indian Ocean) and Lizard Island, GBR (Baird 2000). Hutchins (1999) reported catastrophic mortality of Pocillopora coral at Rottnest Island, Western Australia that could have been caused by disease as it quickly spread through a large area. Previously there had been only one report from Western Australia (Simpson et al. 1993) of coral ‘disturbance’ of any kind, and no previous records of disease-related mortality.

Coral diseases are not necessarily caused by microbes. Metapeyssonnelia corallepida, is a recently described coral-killing red alga on Caribbean reefs (Antonius 1999b) and is one of the causes of the recently described syndromes of epizoism on reef corals particularly on reef crest areas (Antonius and Ballesteros 1998). 

Fossil evidence also seems to suggest that some coral ‘diseases’ are novel. For example, the rapid replacement of the coral Acropora cervicornis with Agaricia in Belize and with Porites in the Bahamas, taken as a ‘signature’ of epidemics, was found to be absent from geologic cores representing several thousand years of reef development (Harvell et al. 1999).

Dust from African deserts may be responsible for spreading disease across the world’s coral reefs. This is facilitated by prolonged drought in the Sahel region since the mid ‘70s has increased by fivefold the amount of atmospheric dust containing bacteria, viruses and fungi that can kill coral (Pearce 1999). Outbreaks of diseases such as white band and black band disease and the bacterial infection known as “coral plague” have coincided with years when the dust load was highest, the Caribbean being particularly badly affected. The strongest evidence for this hypothesis is the spread of a soil fungus, Aspergillus, in the Caribbean. It first appeared in 1983, an exceptionally dusty year, and since then has killed more than 90% of the Caribbean’s sea fans (gorgonian soft corals). Iron in the dust can also trigger algal growth by stimulating nitrogen fixation. Fabricius (pers. comm.) claims that while some workers link this mass mortality to land run off, others suggest it is caused by the fungus Aspergillus (Smith et al. 1996a; Nagelkerken et al. 1997a; Nagelkerken et al. 1997b; Geiser et al. 1998; Harvell et al. 1999).