Land-based epidemics aren't the only thing we should be worried about, says Laura H. Kahn.
Excerpt: Much attention has been paid to newly emergent diseases that have afflicted humans in recent decades--HIV/AIDS, SARS, avian influenza, etc. Conversely, deadly diseases that have emerged in the world's oceans during the same time period have been largely ignored. While these diseases haven't caused epidemics in humans, they have proved troublesome to marine animal populations and to susceptible humans who have ventured into contaminated waters. Therefore, we should pay closer attention to what's happening in the world's oceans since it could be an important sentinel for global environmental health.
Take for instance, recent epizootics (epidemics in animals) of Atlantic Ocean bottlenose dolphins and endangered Florida manatees. They perished because of the neurotoxins produced by Karenia brevis, a marine plankton that lives year-round in the Gulf of Mexico. (See "Emerging Diseases in Marine Mammals: From Dolphins to Manatees." PDF)
A single-celled organism (called a dinoflagellate), K. brevis has two whip-like appendages, or flagella, it uses to swim through the water. The neurotoxins produced by K. brevis can kill fish and birds, as well as marine animals.
When they become aerosolized in sea spray and inhaled by humans, these organisms can cause people to develop respiratory and eye irritations. The toxins can also accumulate in shellfish such as clams, coquinas, and oysters, causing food poisoning in those who eat them. Symptoms usually begin a few hours after ingestion and include tingling and numbness in the tongue, lips, throat, arms, and legs and dizziness, nausea, and diarrhea. The symptoms usually go away after a few days.