Elkhorn coral infected with white pox.

What’s the News: Over the past decade, diseases, pollution, and warming waters have put coral populations across the globe in a dramatic decline. In an extreme case, the population of elkhorn coral, considered one of the most important reef-building corals in the Caribbean, has decreased by 90–95 percent since 1980, partly due to a disease called white pox.

Now, scientists have traced this lethal disease back to humans. Human feces, which seep into the Florida Keys and the Caribbean from leaky septic tanks, transmit a white pox-causing bacterium to elkhorn coral, researchers report in the journal PLoS ONE. “It is the first time ever that a human disease has been shown to kill an invertebrate,” ecologist James Porter told Livescience. “This is unusual because we humans usually get disease from wildlife, and this is the other way around.”

What’s the Context:

Serratia marcescens is a bacterium found in the intestines of humans and many other animals. Resistant to many types of antibiotics, S. marcescens is known to cause respiratory problems and urinary tract infections in people.
The bacteria can also infect coral—in 2002, Porter and his colleagues learned ...