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Yes, Flesh-Eating Bacteria Are in the Warm Coastal Waters – but It Doesn’t Mean You’ll Get Sick

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Yes, Flesh-Eating Bacteria Are in the Warm Coastal Waters – but It Doesn’t Mean You’ll Get Sick

Cover all open wounds with waterproof bandages before swimming in the ocean. lzf / iStock / Getty Images Plus

By Brian Labus

Like humans, many bacteria like to spend time at the beach. The so-called flesh-eating bacteria, Vibrio vulnificus, don't just like the beach; they need it, and rely on sea salt for survival. And as with human beachgoers, the warmer the water, the more of them there are.


V. vulnificus is most commonly found in the warm waters of the states bordering the warm waters of the Gulf of Mexico but can also be found along the Atlantic and Pacific coasts. As ocean temperatures rise, it will spread with those warming waters to new ocean habitats where colder waters previously kept it in check. We have seen outbreaks of disease from similar types of Vibrio related to rising ocean temperatures as far north as Alaska.

Most cases of infection occur between May and October, when coastal waters are warmest. This could change, however, as summer weather starts earlier and lasts longer.

I am an infectious disease epidemiologist interested in tracking disease, investigating outbreaks and food safety. The first large outbreak I worked on in Las Vegas was caused by contaminated oysters, and it made me realize just how easily food from the ocean can show up in the desert and make people sick if it isn't harvested, handled and prepared properly.

We Only Hear About the Worst Cases

News reports tend to focus on people dying or losing limbs from the "flesh eating" bacteria. It's not front-page news when someone has a mild skin infection or eats a bad oyster and spends a couple days in the bathroom. We don't often identify the most mild illnesses because people typically don't seek medical care for them.

Even so, V. vulnificus infections are rare. The Centers for Disease Control and Prevention estimates that about 205 infections occur each year, of which 124 were reported in 2014, including 21 deaths. To put this in some perspective, over 32,000 people died that year in motor vehicle crashes.

Most cases tend to be males over 40 years of age and nearly all of them have some sort of underlying chronic health condition, such as liver or kidney disease, alcoholism or diabetes.

Even for high-risk people, simply swimming alongside the bacteria is not enough to make you sick. The bacteria must find a way to get into your body to multiply and cause damage.

For some people, this involves eating food contaminated by the bacteria – typically raw oysters. Oysters eat by filtering out small particles in the water, including bacteria, so they can contain much higher concentrations of Vibrio than the ocean itself. When someone eats a raw or undercooked oyster, the bacteria can multiply in the gastrointestinal tract and cause nausea and abdominal pain.

It can also lead to a life-threatening infection, as bacteria can move from the intestines into the bloodstream and cause an infection throughout the body. Because it spreads so quickly, it can overwhelm the body before the immune system has a chance to stop the infection. Systemic infections are treatable with antibiotics, but it is important that treatment start quickly, as the death rate can be over 50%.

For other people, V. vulnificus can enter through broken skin such as cuts, burns or wounds. Bacteria can multiply under the skin and cause a life-threatening illness commonly known as flesh-eating disease, or necrotizing fasciitis, which can appear suddenly and spread quickly. The infections typically cause a fever and cause the skin to become, red, swollen and painful at the site of infection. The bacteria do not actually "eat" the flesh, but this is what the disease can look like. Between the growth of the bacteria, the production of toxins, and collateral damage from an overwhelming immune system response, large areas of tissue under the skin can die. The infection is treatable with antibiotics, but it is important that treatment is swift.

So What Can We Do About It?

First, avoid eating raw shellfish, especially if you have a weakened immune system due to liver or kidney disease; are on medications, such as steroids, that suppress the immune system; or are diabetic or have cancer. While raw oysters are a popular delicacy, eating any uncooked animal product carries a risk of disease. If you are preparing oysters at home, handle them just as you would any other raw meat. But keep in mind that lemon juice, hot sauce or alcohol do not kill the bacteria and will not protect you if the shellfish is contaminated and that there is no way to identify the contamination by sight or taste.

Another precaution is not to swim with open cuts or wounds, as this provides a direct path for bacteria to enter your body. Avoid the ocean until you heal or cover the wounds with waterproof bandages.

If you are at high risk for infection because a weakened immune system, wear clothing and shoes that will protect you from cuts and scrapes while swimming.

Finally, if you do wind up with a skin infection after swimming in the ocean or gastroenteritis after eating raw shellfish, tell your doctor, as prompt identification and treatment is necessary for this rare illness.

Remember, you don't need to skip the beach. Just use some common sense measures to protect yourself from infection by V. vulnificus, especially if you are at high risk.

Brian Labus is an assistant professor of epidemiology and biostatistics at the University of Nevada, Las Vegas.
Disclosure statement:
Brian Labus received past funding from the Centers for Disease Control and Prevention for disease surveillance activities while working at the local health department, including the subject of this article.

Reposted with permission from our media associate The Conversation.

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Just in time for Halloween, scientists at Cornell University have published some frightening research, especially if you're an insect!

The ghoulishly named ogre-faced spider can "hear" with its legs and use that ability to catch insects flying behind it, the study published in Current Biology Thursday concluded.

"Spiders are sensitive to airborne sound," Cornell professor emeritus Dr. Charles Walcott, who was not involved with the study, told the Cornell Chronicle. "That's the big message really."

The net-casting, ogre-faced spider (Deinopis spinosa) has a unique hunting strategy, as study coauthor Cornell University postdoctoral researcher Jay Stafstrom explained in a video.

They hunt only at night using a special kind of web: an A-shaped frame made from non-sticky silk that supports a fuzzy rectangle that they hold with their front forelegs and use to trap prey.

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But the spiders can also perform a move called the "backward strike," Stafstrom explained, in which they reach their legs behind them and catch insects flying through the air.

"So here comes a flying bug and somehow the spider gets information on the sound direction and its distance. The spiders time the 200-millisecond leap if the fly is within its capture zone – much like an over-the-shoulder catch. The spider gets its prey. They're accurate," coauthor Ronald Hoy, the D & D Joslovitz Merksamer Professor in the Department of Neurobiology and Behavior in the College of Arts and Sciences, told the Cornell Chronicle.

What the researchers wanted to understand was how the spiders could tell what was moving behind them when they have no ears.

It isn't a question of peripheral vision. In a 2016 study, the same team blindfolded the spiders and sent them out to hunt, Science explained. This prevented the spiders from making their forward strikes, but they were still able to catch prey using the backwards strike. The researchers thought the spiders were "hearing" their prey with the sensors on the tips of their legs. All spiders have these sensors, but scientists had previously thought they were only able to detect vibrations through surfaces, not sounds in the air.

To test how well the ogre-faced spiders could actually hear, the researchers conducted a two-part experiment.

First, they inserted electrodes into removed spider legs and into the brains of intact spiders. They put the spiders and the legs into a vibration-proof booth and played sounds from two meters (approximately 6.5 feet) away. The spiders and the legs responded to sounds from 100 hertz to 10,000 hertz.

Next, they played the five sounds that had triggered the biggest response to 25 spiders in the wild and 51 spiders in the lab. More than half the spiders did the "backward strike" move when they heard sounds that have a lower frequency similar to insect wing beats. When the higher frequency sounds were played, the spiders did not move. This suggests the higher frequencies may mimic the sounds of predators like birds.

University of Cincinnati spider behavioral ecologist George Uetz told Science that the results were a "surprise" that indicated science has much to learn about spiders as a whole. Because all spiders have these receptors on their legs, it is possible that all spiders can hear. This theory was first put forward by Walcott 60 years ago, but was dismissed at the time, according to the Cornell Chronicle. But studies of other spiders have turned up further evidence since. A 2016 study found that a kind of jumping spider can pick up sonic vibrations in the air.

"We don't know diddly about spiders," Uetz told Science. "They are much more complex than people ever thought they were."

Learning more provides scientists with an opportunity to study their sensory abilities in order to improve technology like bio-sensors, directional microphones and visual processing algorithms, Stafstrom told CNN.

Hoy agreed.

"The point is any understudied, underappreciated group has fascinating lives, even a yucky spider, and we can learn something from it," he told CNN.

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