Puerto Rico has coral reefs of remarkable beauty. What many people do not know is that these organisms are extremely delicate and susceptible to viruses, bacteria, and other infectious microorganisms. As in humans, corals have an immune system that helps them fight off infections, but little is known about how it works. A group from the University of Puerto Rico, Rio Piedras studied the immune system response of the sea fan coral and developed a mathematic model to simulate how this coral responds to common infections.