"This is the first time, to our knowledge, that a bacterial species associated with the human gut has been shown to be a marine invertebrate pathogen," they wrote in their report, published in the Proceedings of the National Academy of Sciences.

The researchers, led by Kathryn Patterson and James Porter of the University of Georgia, said the disease white pox is killing Caribbean elkhorn coral.

The coral, known scientifically as Acropora palmata, lives in warm, shallow water and 70 percent of the colonies of tiny organisms have been killed off the Keys.

White pox spreads rapidly and is highly contagious. Patterson's team said they discovered the cause of the disease is Serratia marcescens, a bacteria commonly found in the guts of people and animals.

They sampled 40 coral reef sites in the Florida Keys National Marine Sanctuary and found the A. palmata coral at seven of them. They first videotaped the coral in 1996.

Within just a year they found white pox disease at all seven places. "Once white pox appeared on a reef, it spread to all four stations on that reef within one year," they wrote.