A strange new menace has joined the long list of threats to corals, the tiny reef-building animals that create important habitat in our oceans.

A bacterium that attacks humans is also killing off a species of coral in the Caribbean, elkhorn coral, according to researchers who proved the link by infecting fragments of the coral with bacteria from human sewage.

‘This is quite an unusual discovery. It is the first time ever that a human disease has been shown to kill an invertebrate,’ said University of Georgia professor James Porter, one of the study researchers. ‘This is unusual because we humans usually get disease from wildlife, and this is the other way around.’

In humans, the pathogen Serratia marcescens is opportunistic, causing respiratory, wound and urinary tract infections. In coral, it causes a disease Porter and colleagues have dubbed ‘white pox’ for the white scars that appear on infected elkhorn coral. These scars appear where the coral’s living tissue has disappeared, leaving only its skeleton.

Worldwide coral faces a litany of threats. Hurricanes, which are predicted to increase in severity and number as a result of climate change, break coral to bits; warming water temperatures cause it to eject its photosynthetic algae and to […]