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.
Flesh-Eating Bacteria Infects Three as Experts Warn Warming Oceans Could Make It More Common https://t.co/jsdOZPPsYQ— Enviro Voter Project (@Enviro_Voter) July 10, 2019
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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When hurricanes and other extreme storms unleash downpours like Tropical Storm Beta has been doing in the South, the floodwater doesn't always stay within the government's flood risk zones.
New research suggests that nearly twice as many properties are at risk from a 100-year flood today than the Federal Emergency Management Agency's flood maps indicate.
Flooding Outside the Zones<p>About <a href="https://furmancenter.org/files/Floodplain_PopulationBrief_12DEC2017.pdf" target="_blank">15 million</a> Americans live in FEMA's current 100-year flood zones. The designation warns them that their properties face a 1% risk of flooding in any given year. They must obtain flood insurance if they want a federally ensured loan – insurance that helps them recover from flooding.</p><p>In Greater Houston, however, <a href="https://doi.org/10.1111/j.1539-6924.2012.01840.x" target="_blank">47% of claims</a> made to FEMA across three decades before Hurricane Harvey were outside of the 100-year flood zones. Harris County, recognizing that FEMA flood maps don't capture the full risk, now <a href="https://www.hcfcd.org/floodinsurance" target="_blank" rel="noopener noreferrer">recommends that every household</a> in Houston and the rest of the county have flood insurance.</p><p>New risk models point to a similar conclusion: Flood risk in these areas outstrips expectations in the current FEMA flood maps.</p><p>One of those models, from the <a href="https://firststreet.org/flood-lab/research/2020-national-flood-risk-assessment-highlights/" target="_blank">First Street Foundation</a>, estimates that the number of properties at risk in a 100-year storm is 1.7 times higher than the FEMA maps suggest. Other <a href="https://doi.org/10.1088/1748-9326/aaac65" target="_blank" rel="noopener noreferrer">researchers</a> find an even higher margin, with 2.6 to 3.1 times more people exposed to serious flooding in a 100-year storm than FEMA estimates.</p>
What FEMA’s Flood Maps Miss<p>Understanding why areas outside the 100-year flood zones are flooding more often than the FEMA maps suggest involves larger social and environmental issues. Three reasons stand out.</p><p>First, some places rely on relatively old FEMA maps that don't account for recent urbanization.</p><p>Urbanization matters because impervious surfaces – think pavement and buildings – are not effective sponges like natural landscapes can be. Moreover, the process for updating floodplain maps is locally variable and can take years to complete. Famously, New York City was updating its maps when Hurricane Sandy hit in 2012 but hadn't finished, meaning flood maps in effect <a href="https://projects.propublica.org/nyc-flood/" target="_blank">were from 1983</a>. FEMA is required to assess whether updates are needed every five years, but the <a href="https://www.fema.gov/cis/nation.html" target="_blank" rel="noopener noreferrer">majority of maps</a> <a href="https://www.oig.dhs.gov/sites/default/files/assets/2017/OIG-17-110-Sep17.pdf" target="_blank" rel="noopener noreferrer">are older</a>.</p><p>Second, binary thinking can lead people to an underaccounting of risk, and that can mean communities fail to take steps that could protect a neighborhood from flooding. The logic goes: if I'm not in the 100-year floodplain, then I'm not at risk. Risk perception <a href="https://doi.org/10.1088/1748-9326/ab195a" target="_blank" rel="noopener noreferrer">research</a> backs this up. FEMA-delineated flood zones are the major factor shaping flood mitigation behaviors.</p><p>Third, the era of climate change scuttles conventional assumptions.</p><p>As the planet warms, extreme storms are becoming <a href="https://nca2018.globalchange.gov/" target="_blank">more common and severe</a>. If greenhouse gas emissions continue to increase at a high rate, computer models suggest that the chances of a severe storm dropping 20 inches of rain on Texas in any given year will increase from about 1% at the end of the last century to 18% at the end of this one, a chance of <a href="https://doi.org/10.1073/pnas.1716222114" target="_blank" rel="noopener noreferrer">once every 5.5 years</a>. So far, <a href="https://www.rstreet.org/wp-content/uploads/2020/02/195.pdf" target="_blank" rel="noopener noreferrer">FEMA hasn't taken into account the impact climate change is having</a> on extreme weather and sea level rise.</p>
Racial Disparities in Flooding Outside the Zones<p>So, who is at risk?</p><p>Years of research and evidence from storms have highlighted social inequalities in areas with a high risk of flooding. But most local governments have less understanding of the social and demographic composition of communities that experience flood impacts outside of flood zones.</p><p>In analyzing the damage from Hurricane Harvey in the Houston area, I found that <a href="https://doi.org/10.1088/1748-9326/aba0fe" target="_blank">Black and Hispanic residents disproportionately experienced flooding</a> in areas beyond FEMA's 100-year flood zones.</p><p>With the majority of flooding from Hurricane Harvey occurring outside of 100-year flood zones, this meant that the overall impact of Harvey was racially unequal too.</p><p>Research into where flooding occurs in Baltimore, Chicago and Phoenix points to some of the potential causes. <a href="https://www.nap.edu/read/25381/chapter/4#16" target="_blank" rel="noopener noreferrer">In Baltimore and Chicago</a>, for example, aging storm and sewer infrastructure, poor construction and insufficient efforts to mitigate flooding are part of the flooding problem in some predominantly Black neighborhoods.</p>
What Can Be Done About It<p>Better accounting for those three reasons could substantively improve risk assessments and help cities prioritize infrastructure improvements and flood mitigation projects in these at-risk neighborhoods.</p><p>For example, First Street Foundation's risk maps account for <a href="https://firststreet.org/flood-lab/research/flood-model-methodology_overview/" target="_blank">climate change</a> and present <a href="https://floodfactor.com/" target="_blank" rel="noopener noreferrer">ratings</a> on a scale from 1 to 10. FEMA, which works with communities to update flood maps, is <a href="https://www.fema.gov/media-library-data/1521054297905-ca85d066dddb84c975b165db653c9049/TMAC_2017_Annual_Report_Final508(v8)_03-12-2018.pdf" target="_blank" rel="noopener noreferrer">exploring rating systems</a>. And the National Academies of Sciences, Engineering and Medicine recently <a href="https://www.nationalacademies.org/news/2019/03/new-report-calls-for-different-approaches-to-predict-and-understand-urban-flooding" target="_blank" rel="noopener noreferrer">called for a new generation of flood maps</a> that takes climate change into account.</p><p>Including recent urbanization in those assessments will matter too, especially in fast-growing cities like Houston, where <a href="https://authors.elsevier.com/a/1boBRyDvMFW6W" target="_blank" rel="noopener noreferrer">386 new square miles</a> of impervious surfaces were created in the last 20 years. That's greater than the land area of New York City. New construction in one area can also <a href="https://scalawagmagazine.org/2018/01/city-in-a-swamp-as-houston-booms-its-flood-problems-are-only-getting-worse/" target="_blank" rel="noopener noreferrer">impact older neighborhoods downhill</a> during a flood, as some Houston communities discovered in Hurricane Harvey.</p><p>Improving risk assessments is needed not just to better prepare communities for major flood events, but also to prevent racial inequalities – in housing and beyond – from <a href="https://www.npr.org/2019/03/05/688786177/how-federal-disaster-money-favors-the-rich" target="_blank" rel="noopener noreferrer">growing</a> after the unequal impacts of disasters.</p>
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