What do you think about the safety of swimming at the beach these days? Between the flesh-eating bacteria and the sharks, should we just sun on the beach and only swim in a pool?



Dear Worried,

Please keep in mind that events make the news because they are unusual. Although terrifying, both human shark bites and “flesh eating bacteria” infections are very unusual.

1) Flesh-eating bacteria – The medical name for these rare infections is necrotizing soft tissue infection, or NSTI. The term necrotizing comes from necrosis, which means death of an area of body tissue. Soft tissue means skin and the areas just below the skin: fat, muscle, and connective tissues (tendons and ligaments). Another medical term for these infections is necrotizing fasciitis, which refers to destruction of the fascia, the connective tissue sheaths that cover muscles.

Even though there may have been more episodes of necrotizing infections than usual this year, there are still only two cases per million people per year in the US, or one in 500,000. I have seen just one case in my 30-year career; many doctors will never see one.

The visible tissue damage is what makes necrotizing infections so frightening. All deadly infections cause tissue damage, but it usually happens inside the body where it can’t be seen. If the damaged lungs of a person dying from pneumonia could be seen, it would be just as disturbing. Pneumonia is much more common than necrotizing infections – every primary care practitioner will have patients who die of pneumonia – but it is much less feared.

Necrotizing infections are caused by bacteria that normally live in seawater. Two of the commonest are group A streptococcus (GAS) and Vibrio vulnificus. Often, several different types of bacteria are present. Infections develop after bacteria enter the bloodstream through breaks in the skin such as cuts, scrapes, burns, insect bites, and puncture wounds. People also can get these infections from eating raw oysters contaminated with bacteria. Strangely, these infections also can occur after a fall, muscle strain, or other injury that does not break the skin. The early signs of infection are a spreading area of tenderness, loss of sensation, swelling or redness in or below the skin, even if there is no obvious break in the skin. Necrotizing infections most often occur on the legs or arms, but can occur in any part of the body. These infections can be treated with antibiotics if diagnosed early. The infection develops very fast, often within hours. Surgery often is needed to remove infected skin and connective tissues.

Steps you can take to further lower the small risk of getting a necrotizing infection from seawater:

  • Avoid contact with ocean or bay water if you have open cuts, a rash, or any breaks in your skin
  • Avoid walking barefoot near the water: sand is abrasive and you can easily get small cuts from shells and pebbles
  • Rinse off in fresh water after swimming, sitting or wading in seawater
  • Wash your hands and arms well after fishing or touching raw seafood
  • Do not eat raw oysters
  • If you do get seawater into a cut or abrasion, wash the area well with soap and water. Check the area every couple of hours for the next day or two. Get immediate medical attention if there is an increasing area of tenderness, numbness, swelling or redness. It’s important to know that if the infection is mainly below the skin, the skin may look normal but the area can be tender to touch or numb (no sensation when touched).
  • Healthy people of any age can get necrotizing infections, but those with weaker immune systems are at greater risk. This includes infants and toddlers, the elderly, and people with chronic diseases such as diabetes, liver disease, and poor circulation.

2) Sharks – On average, there are 19 shark attacks per year in the US, with one death from shark bite every two years.

The odds of getting attacked and killed by a shark are one in four million.

There is a much greater chance – one in 63 – of dying from the flu than from a shark bite. (Still, lots of people won’t get a shot to prevent the flu!)

One in five Americans dies of heart disease, one in 24 from a stroke, one in 84 in a car accident. As rare as it is to be killed by lightning (one in 80,000 people) it is still 50 times more likely than death from shark bite. You are eleven times more likely to die from fireworks (one in 341,000) than from shark bite, but fireworks are still easily available.

For every person killed by a shark each year (about five worldwide), people kill over two million sharks. That’s over 20,000 sharks killed every hour, over 300 every minute. Most of them are killed just for their fins, to make shark’s-fin soup. The fins are cut off and the shark is thrown back into the ocean to bleed to death. Clearly we are a much bigger danger to sharks than sharks are to us.

So overall, if you are not too frightened to get into a car to go out to dinner or visit a friend, you shouldn’t worry about the far smaller risk of a shark bite.

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Dr. Eva Hersh, MD
Dr. Eva Hersh, MD
Eva Hersh is a family physician. Send your comments and questions to her by email at dreva@baltimoreoutloud.com