In the summer, as coastal waters warm up, so does the presence of a bacterium that can cause serious infections in humans. It is Vibrio vulnificus, a microorganism that lives naturally in marine waters and can enter the body through an open wound. The US state of Louisiana has recorded nine cases of infection this year, five of which have resulted in the death of those affected. All have required hospitalization and authorities have linked them to exposure of wounds to seawater. In the previous ten years, the state had recorded an average of seven cases and one death annually.