Ask the Doctors

Dear Doctor: Every now and then I read about a death related to "flesh-eating bacteria" that was contracted in water of some sort. The most recent one was in the floodwaters of Hurricane Harvey, near Houston. How does this happen? Is there anything we can do to stay safe?

Dear Reader: When we talk about flesh-eating bacteria, we're really talking about necrotizing fasciitis, a serious skin infection that can be caused by one of several different types of bacteria. The bacterium enters the body through a break in the skin -- anything from an insect bite to a scrape, scratch or open wound -- and then rapidly spreads through the body's soft tissue.

Contrary to their name, these bacteria don't actually eat the flesh. However, they do kill it. The word "necrotizing" means "causing the death of tissues." The word "fasciitis" refers to the fascia, which is the connective tissue that surrounds muscles, fat, blood vessels and nerves.

As for the bacteria themselves, group A strep is the most common cause. Other possibilities include E. coli, staph (aka Staphylococcus aureus), Klebsiella, Clostridium and Aeromonas hydrophila. In the case of Harvey's floodwaters, which included seawater, the marine bacterium Vibrio is also a possible culprit.

Although several cases of necrotizing fasciitis came to light due to contact with the contaminated floodwaters of Hurricane Harvey, the condition is rare. About 700 cases are diagnosed per year in the United States. In fact, many people exposed to the bacteria that cause it are not affected. According to the Centers for Disease Control and Prevention, those who do contract it often have weakened immune systems due to conditions like diabetes, cancer, chronic lung, heart or kidney disease, or autoimmune diseases like lupus.

There is no surefire way to prevent necrotizing fasciitis. That means the best defense is using good wound care techniques. For example:

-- Never delay first aid for a wound, even if it's minor or not infected. A blister, scrape or any break in the skin should be cleaned, disinfected and covered.

-- If you do have an open wound, or one that is draining, always keep it covered with clean and dry bandages until it is healed.

-- If you have an open wound or a skin infection, steer clear of enclosed systems like hot tubs, swimming pools or whirlpools. You should also avoid contact with natural bodies of water, like rivers, lakes, ponds and oceans.

Vigilance is key. Necrotizing fasciitis moves swiftly. Unlike a typical infection, which develops over the course of days, the symptoms of necrotizing fasciitis begin within hours.

Many patients report experiencing pain that is more severe than expected for the size of their wound. Ulcers, blisters or black spots may appear. The skin may feel quite warm, with areas of swelling that have a reddish or purple cast. Later, flulike symptoms including chills, fever, extreme fatigue and vomiting may appear.

Successful treatment depends on the earliest-possible intervention. Even then, broad-spectrum antibiotics and surgical debridement may not stop the infection. In some cases, amputation becomes the only option to save the patient's life.

If after performing first aid you are concerned about a wound, or simply feel better being hypervigilant, use a pen to outline the borders of redness when any infection appears. If the infection grows beyond those borders in the course of hours, seek out medical help immediately.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

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