February 1, 2023
Annapolis, US 33 F

Chesapeake Bay: Safe to Swim?


Health Risks of Swimming in the Chesapeake Bay

Is it safe to swim in the Chesapeake Bay? What kind of diseases are out there and what’s the chance you’ll get something?  We review what you can get, from where and how to avoid getting any of it.

Safely swimming in the bay is not impossible and one can avoid many infections following these 5 simple rules:

1. Check the Water Quality! Anne Arundel County Department of Health Water Quality Program is the best resource. Do not swim in the Bay before checking this site.

2. After rainfall of 1/2 inch or more, all Anne Arundel County beaches are under a no swimming/no direct water contact advisory for at least 48 hours. Also, do not swim in cloudy, murky water.

3. Do not swim in the Bay if you have an ear infection, a perforated eardrum, open cuts, scratches or skin lesions, or a compromised immune system.

4. Do not swim in water areas where there is a fish kill or where there are any dead animals or known algae bloom.

5. Try not to swallow water while swimming

If you follow those 5 simple rules, you lower your risk for getting a water-related disease dramatically.


Water Related Illnesses

So what’s out there? The CDC uses the term Recreational Water Illnesses (RWIs). RWIs are caused by germs spread by swallowing, breathing in mists, or having contact with contaminated water.  RWIs can be a wide variety of infections, including intestinal, skin, ear, lungs, eye, nervous system and wound infections.

The most commonly reported RWI is diarrhea. Diarrheal illnesses can be caused by germs such as Crypto (short for Cryptosporidium), Giardia, Shigella, norovirus and E. coli O157:H7.

In 2009, the Chesapeake Bay Foundation published a PDF claiming, “The Chesapeake Bay in summer is like a warm pond with a broth of nutrients at the right temperature to breed algae and bacteria.” We’ll briefly explore a few of these now.

Vibrio (“Flesh Eating Bacteria”)

This bacterial infection is often referred to, in the press, as the “flesh eating bacteria”. There are several

species of Vibrio. Vibrio vulnificus causes severe skin ulcers, gangrene, and deadly blood infections in people who expose cuts to warm saltwater containing the bacteria, as well as gastrointestinal illnesses in people who eat tainted shellfish.

Another species, Vibrio parahaemolyticus, causes diarrhea, vomiting, and skin infections, but is seldom deadly. The best known is Vibrio cholerae which causes cholera, a diarrheal disease now virtually eliminated from the United States.

Harmful Algal Blooms and Cyanobacteria

One toxin-producing form of algae, called blue-green algae, is not really algae at all, but rather a class of bacteria, called cyanobacteria. There are at least 35 types of algae in the Chesapeake Bay that produce toxins. The most well known, Blue-green (Microcystis), is the cause of most blooms and fish kills reported.

A 2008 study reported that between 2000 and 2006, 31 percent of the waters tested with blue-green algal (cyanobacteria) blooms had enough toxins to make them unsafe for children to swim in.

According to the World Health Organization, Cyanobacterial toxins are classified by how they affect the human body. Some will affect the liver, nervous system or intestinal systems. Some symptoms can include skin irritation, stomach cramps, vomiting, nausea, diarrhea, fever, sore throat, headache, muscle and joint pain, blisters of the mouth and liver damage. Swimmers in water containing cyanobacterial toxins may suffer allergic reactions, such as asthma, eye irritation, rashes, and blisters around the mouth and nose.

Mycobacterium marinum (M. marinum)

Infections due to M. marinum usually follows a cut or trauma while in the water or

exposure of traumatized skin to aquariums or natural bodies of water. The average incubation period (time between being in the water and showing signs of infection) was 21 days (but the range was anywhere from 5 to 270 days).

M. marinum lesions are slow growing and typically affect the elbows, knees, and backs of feet and hands. The infection can look like either nodules (image left) or shallow ulcers (image right). M. Marinum usually requires a very long course of antbiotics–sometimes for months and can take up to a year to resolve.

What if I swallow some water?

If you accidentally swallow water, your at risk of developing any one of a number of diarrhea-causing infections. These range from Crypto (short for Cryptosporidium), Giardia, Shigella, norovirus to E. coli O157:H7. If you develop diarrhea within 2-7 days, particularly if it is bloody or associated with fever or lasts for longer than 48 hours or is associated with abdominal pain, you should go contact your doctor or go to an urgent care center.

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  1. So, the conditions have to be perfect and you have to have absolutely perfect form in every aspect of swimming.

    This entire article could have been summed up by saying, “IChesepeake Bay: Safe to Swim? No. No, it isn’t.”

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