When you go into the water, the water goes into you too— into your eyes, nose, ears, mouth, and open wounds. Many state laws require beaches to close if tests show dangerous levels of bacteria. But Joan Rose, professor of water pollution microbiology at the University of South Florida College of Marine Sciences, studies another threat— viral infection— that usually goes unmentioned. Recreational waters off California, Florida, and other coastal states show surprising concentrations of viruses that can cause maladies ranging from gastrointestinal distress to possibly fatal myocarditis. Discover contributing editor Jack McClintock talked with Rose about the danger in the waves.
How do viruses get into the oceans near our beaches?In California, mostly as runoff from storm drains. In the Florida Keys, infected water leaches from septic tanks and sewer lines, or is washed into the ocean by thundershowers. There's an amazing interchange between groundwater and adjacent surface water, such as a canal or lake. In Key Largo, we flushed virus tracers down toilets and found them 24 hours later in canals 10 to 20 yards away. Then the tides washed them out toward the reef.
How widespread is the problem?We don't know how prevalent virus infections are, but someone in the community is always infected and excreting these viruses because we can always find them in sewage. We find more viruses in winter when the water is cooler— that's probably related to their survival— and when it rains. Overall we've detected human viruses at more than 60 percent of the coastal sites we've tested.
Is this a serious public health risk?Key West had an event where people would swim around the island. They canceled it last year because of water quality. Two years ago, 30 percent of the participants reported gastric, skin, eye, or respiratory symptoms. So there's definitely a risk. We've stressed our coastal environment around the world.
Does wastewater pose a threat to aquatic wildlife as well?Fish can get infected with Aeromonas and other bacteria. Upsets in the ecosystem may lead to toxic algae that could also be a problem for fish. We need to know much more about the ecology of water— estuarine, ocean, groundwater, even water in pipes.
What's the next step for your research? We'd like to learn when and where we're at risk by understanding land-use and transport patterns and by tracking virus sources. We'd also like to take a beach or two, create circulation models, and see if we can get some kind of predictability. We want to be able to tell the public what we think is going on so they can make the judgment for themselves. In the long run, we need better storm-water management.
Do you take any precautions when you go to the beach?I pay attention to state evaluations of beaches. I don't like to swim in natural waters in certain countries. I don't swim in canals next to areas with septic tanks. I try to avoid very crowded beaches, because they can have greater pollution.
Do you ever feel grim working with sewage and germs?Actually, I love it.
