Surf's Up for Pathogenic Viruses and Bacteria, Too

A day at the shore can leave beachgoers with more than a sunburn — a gulp of seawater can expose swimmers to disease-causing microbes like norovirus, salmonella, and adenovirus. Marine scientist Rachel Noble and environmental medicine researcher Samuel Dorevitch discuss the risk, and what's being done to limit swimmers' exposure.

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IRA FLATOW, HOST:

Just when you thought it was safe to go into the water - you remember that music, of course. It now appears it's not only the sharks you have to worry about, but tiny microbes, things like norovirus, enterovirus, adenovirus, and salmonella - just a few of the nasties that have no menacing dorsal fins or big teeth, but might be found surfing the waves along with you, and if you're unlucky, might give you stomach cramps, fever, nausea, diarrhea. It happened to one of our staff members right here on SCIENCE FRIDAY.

How serious is the risk, and how do they get into the coastal waters? And is there anything we can do to keep these microbes out of the water? Rachel Noble is a professor at the Institute of Marine Sciences at the University of North Carolina-Chapel Hill. She's based in Morehead City, North Carolina. Welcome to SCIENCE FRIDAY, Dr. Noble.

RACHEL NOBLE: Thank you, Ira. I love the music.

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FLATOW: You must get that a lot, that music, I imagine?

NOBLE: Absolutely. Noroviruses are every bit just as dangerous.

FLATOW: Is that right? Are they that dangerous?

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NOBLE: No, no, because - no. They might cause a little discomfort for a day or so, but I don't think that that would prolong for as long as any of the nasties that would occur after some kind of an attack. But anyway...

FLATOW: Yeah, well let's talk about what nasties besides norovirus, what things should be worried about, or should we not be worried about in the water there?

NOBLE: Well, there's a few things that people have been studying in water, water-borne pathogens. Those are things that are making people sick that are in the water, and those would be viruses, bacteria and also could be protozoa, which are just small, microscopic organisms that are not either viruses or bacteria.

You already mentioned the norovirus. Norovirus is one of the ones that people are very familiar with, because of the news. They're the ones that have been problems on cruise ships. Also with the super bugs this spring, it's just a very infectious virus. It's very contagious from person to person.

FLATOW: I want to bring on Samuel Dorevitch. He's an occupation and environmental medicine specialist at the University of Illinois in Chicago. Welcome to SCIENCE FRIDAY.

SAMUEL DOREVITCH: Thanks, Ira.

FLATOW: How many people would you say get sick from swimming at the beach? Put this in perspective for us, would you.

DOREVITCH: Well, that's a good question, and it's a question that we only have estimates for, no real solid numbers. It seems that about maybe for every 1,000 people who go to the beach, about 50, 60, 70 will get sick, and of those about 20 or 30 per thousand got sick because of their beach exposure.

FLATOW: Would they think it's from the water, or would they think, oh, I had some bad shrimp or something?

DOREVITCH: Exactly. That's one of the big issues that makes it difficult to do surveillance, to do public health work, to figure out the scale of the problem. People may not recognize it as having been linked to the water. People who are at a beach may see - many people at the beach may get sick, but they'll go to different physicians who, unbeknownst to one another, are seeing people who have a related problem.

So it's very difficult, and most of what we do know about rates of illness comes from epidemiologic studies.

FLATOW: We're going to take a break and come back and talk more with Rachel Noble and Samuel Dorevitch. Our number: 1-800-989-8255. What about the beach this summer? What should we be worried, or what should we not be too worried about, but be ready when it strikes? Stay with us. We'll be right back after this break.

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FLATOW: I'm Ira Flatow, this is SCIENCE FRIDAY, from NPR. I'm Ira Flatow. We're talking this hour about the viruses and bacteria that end up in our coastal waters, and talking with Rachel Noble and Samuel Dorevitch. Dr. Noble, where do these things come from? How do they get into the ocean?

NOBLE: Well, in the United States, I would say that the main source is really storm water. And that's the water that's coming from rainfall that's really washing over the land and taking everything with it to the lowest point, which is often a river, a creek or the oceans. Our sewage systems in the United States are quite good, and some of the best in the world in terms of their treatment of things that could make you sick.

So while there are sewage spills every once in a while and cracks in sewage lines, storm water is really one of the biggest sources. So any time you see a pipe that's coming to the beach with water flowing out of it, and in many cases, those are storm water pipes. And if it's flowing after a big rain fall event, likely that it could be containing some material that might be contaminated from washing over the land.

FLATOW: But, you know, that's where you see the kids always playing that water at the beach.

NOBLE: Absolutely. That's one of our largest concerns. So those pipes - remember, even if there's water flowing in that's not from a pipe and that's pooled and coming into the ocean, if it's flowing, you know, from a landward source towards the ocean, it can contain any kinds of material from feces that can come from birds and dogs and people. And those are the things that are going to contain the pathogens that will make people sick.

FLATOW: The National Resource Defense Council, the NRDC, just released their testing the waters report on 20,000 beach closings around the nation last year due, in part, to bacterial contamination. And they wrote, quote, "serious water pollution persists at our nation's beaches." Would you disagree with that?

NOBLE: No, I wouldn't disagree with it. It depends on how much monitoring the state actually does in order to kind of pick up when the beach might be closed. But yes, there are serious problems with some of the - a lot of the storm water that comes to our beaches remains untreated. It's doesn't go through any kind of treatment plant. It's just raw material that's flowing across the land to the ocean. So that can definitely be the case.

FLATOW: Actually, they have a really interesting map. We have a link on our website to a map where you can look up your own beach and see where the water quality, what water quality they have rated. It's sciencefriday.com/beaches. Dr. Dorevitch, these pathogens, I understand, can also be found in the sand at the beach.

DOREVITCH: That's right.

FLATOW: So if you're making a sandcastle, you're playing with the pathogens.

DOREVITCH: That is correct. There's been research in the last few years showing that various viruses and bacteria persist and replicate in sand, and that epidemiologic studies have shown that people who have been digging in sand or have been buried in the sand are at greater risk for getting sick after their beach visit.

FLATOW: We're not telling everybody not to go to the beach, are we?

DOREVITCH: We're definitely not telling people that. We're telling people that they should pay attention to information that's available online about beach quality before they get to the beach. A lot of cities and municipalities post water quality online. Once they get to the beach, they should check if there's a yellow flag or red flag up.

They should wash their hands before they eat after being at the beach. So people definitely should be encouraged to put on their sun block and get out to the beach, but pay attention to the information about risk.

FLATOW: Dr. Noble, what can you do to minimize? Let's say you're in the water and you want to splash around. What can you do while you're in the water to minimize taking in these meanies?

NOBLE: Well, I'm a big swimmer, so it's hard for me to say. But one of the things that people can do is try not to overly ingest huge amounts of water. Of course, whenever you're swimming, the benefit of, you know, the health of just being out in the water and enjoying yourself is going to also somewhat outweigh the risk, especially if the water quality is good.

But head emersion and getting - basically allowing those pathogens to get into either your nose or your mouth are the ways, primarily, that these organisms do make you sick. You have to ingest them in order to make yourself sick with most of them. So the bottom line is trying to not ingest huge amounts of water, and that's probably one of the biggest pieces of guidance.

But one of the pieces of guidance that I give people additionally is just not allowing their families and children to play close to storm drain pipes and in areas where there's pooled water from the land coming into the ocean, because that's often the location of some of the highest risk. And like Sam said, if there are signs, you know, be wary of the signs and be mindful, because many of the signs that are placed near storm drains have been placed and placed around the storm drains to warn people.

And there's been good science conducted behind the signs that allow us to determine how far from storm drains, for example, it might be safe then to swim. There's more yet to done, but I think that a lot of those warning signs are placed, you know, are really placed properly. And so looking out for storm drains is really another piece of advice that I can give.

FLATOW: How long does it take - if you test the water, how long does it take to know that the beach is contaminated?

NOBLE: That's a great question. Right now, the majority of managers, states across the country, they use a test where if you take the sample on a Monday morning, you don't actually get the result until a Tuesday morning. There have been new guidance, basically, released by the EPA just in the last six to nine months that allow the use of some new DNA-based methods, methods that we've actually been, you know, developers of in my laboratory.

And we've been working on these rapid methods for a long time. And so now we can get results in about three hours. And there are states across the country, including California and Virginia, and a range of other states, including some inland locations in Wisconsin, Ohio and in Illinois that have been using these rapid methods to allow us to put signs up now within a few hours, rather than waiting a day past the time whenever the person was in the water.

So now, really, if we take a water sample in the morning, we can get a sign up or notification to the public hopefully before they put their towel down on the beach at roughly noon, or slightly before that, which is a huge advancement. We'd like it to be five minutes, but it's a huge advancement from where we were just a few years ago.

So we hope that the rapid methods will actually improve our ability to warn and notify the public of an event of contamination much more accurately coming into the future.

FLATOW: Let me go to the phones now. Let's go to Gulf Shores, Alabama. Hi Mary. Welcome to SCIENCE FRIDAY.

MARY: Hi, how are you? And thanks for your program.

FLATOW: You're welcome.

MARY: I have a question. It is related to bacteria count, and our beaches, in Gulf Shores, have very good ratings because they test often and apparently have done very well. But what I have been concerned about is the use of dispersants that was allowed by the EPA, and of course that meant the oil was dispersed, and there is probably still dispersant in the water. And, of course, the dispersant, as far as I have heard, disables the microbe eating - the oil-eating microbes from doing their job.

And I've also heard that use of dispersant increased the toxicity of tar balls, or bacteria count. I don't know which. But, anyway, I'd like your comments on how can we test for dispersants, because I'm very comfortable with the bacteria counts, but I'm very concerned. Are we testing for dispersants? And I think we should be, but because of the ingredients.

FLATOW: Sam Dorevitch?

DOREVITCH: Well, I think the caller raises an important issue, that when the water is tested routinely at beaches, it's for a very limited number of analyses. In Great Lakes waters, it's for the e-coli bacteria, and for marine waters it's the Enterococci bacteria. But chemicals are rarely tested, so the idea that more testing for chemicals is right on target, particularly after there's been a known use, heavy use of a chemical in a beach.

But the studies, human health studies are lacking at this point in terms of the particular dispersants that were used in the Gulf oil spill in terms of what do they do to people at beaches.

FLATOW: Thanks for the call, Mary.

MARY: Thank you.

FLATOW: 1-800-989-8255 is our number. Let's go to Nick in Riverside, California. Hi, Nick.

NICK: Hello. Thank you for your show today. The reason for my phone call is it's partially to do with public beaches, but more so, in the State of California this summer, there was a new mandate for signs that were posted on all public swimming areas, including swimming pools. And the signs have to say something along the lines of no swimming allowed by occupants suffering from diarrhea within two weeks.

And this is including, like, public beaches, or also, you know, chlorinated pools. And I'm just curious if this is sort of a very big concern for these pathogens. Is this something new, that as far as for like someone who had, you know, a bad flu two weeks ago, that chlorine can't even kill it?

FLATOW: Dr. Noble, Dr. Dorevitch?

NOBLE: It's not.

DOREVITCH: No. That's...

NOBLE: It's not necessarily new. Sam, I'll let you answer this question. I think one of the biggest things is that for the viral pathogens, you can actually shed them for very long periods of time. So if you have gotten an infection, there's, you know, many studies that demonstrate, you know, people being able to shed them through fecal contamination for 12, 14, 16 weeks, and even longer.

And some of these organisms are extremely hardy in water, even chlorinated water, to be honest. Hepatitis A is a good example. Adenovirus is also another hardy virus. So only in certain circumstances will they actually be degraded so that they wouldn't infect another person.

DOREVITCH: And just to add to that, there are more recorded outbreaks of waterborne disease in chlorinated waters than in surface waters. And that sounds a little paradoxical, but it's because we know more about what happens to people after they've been in a swimming pool.

And the parasites giardia and cryptosporidium, especially cryptosporidium, are very difficult to get rid of with chlorine. So public health authorities have been mounting an education campaign to get people to stay out of the water and prevent them from transmitting, potentially, their cryptosporidium to other people who are in the same swimming pool. So I think they're on the right track by encouraging that in California.

FLATOW: So if you were to choose between the pool and the shore...

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FLATOW: I know what I would choose.

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NOBLE: If it's not raining...

FLATOW: If it's not raining - well, let's...

NOBLE: ...the beach is a great option.

FLATOW: Well, let's talk about rain. Should there be a rule of thumb of how long to wait to go to the beach after a big rain?

NOBLE: There are actually are. In many states, they use one of two approaches. One is that they can say that after a certain amount of rainfall, that it's recommended that - that swimming is not recommended, specifically in places that are prone to a lot of storm drain discharge. So in the state of California, in various places, they have, after a half-an-inch of rain, a warning or a recommendation to the public for a 72-hour kind of watch on water quality in certain areas, once again, that are prone to these freshwater outlets or storm drains.

Other places will use a presumptive rainfall closure, actually, where they say after - rather than a recommendation, where they actually say that a water body is closed after, say, an inch, or an inch and a half of rain will be a more common number for the Atlantic Coast. Once that rainfall amount has been surpassed, they say this beach is closed for 24 hours or so.

FLATOW: Well, I was headed to the beach this weekend. I have to - no, I'm going go out to the beach. I love the beach. Thank you. Thank you both for some very interesting information for us.

DOREVITCH: Thank you.

FLATOW: Have a - and have a great weekend. Rachel Noble, professor at the Institute of Marine Sciences, University of North Carolina-Chapel Hill and Samuel Dorevitch, occupational and environmental medicine specialist, University of Illinois in Chicago. Thanks again for joining us today.

NOBLE: Thank you, Ira. Thanks for the opportunity.

FLATOW: You're welcome. I'm Ira Flatow. This is SCIENCE FRIDAY, from NPR.

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