Merck Manuals Releases Steps to Preventing Waterborne Illnesses

Thursday, August 11, 2016 General News
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Infectious Disease Expert Offers Insight on Hidden Dangers in the Water

KENILWORTH, N.J., Aug. 11, 2016 /PRNewswire/ -- The increased attention on water sanitation issues in Rio has raised

a lot of questions about water-related illnesses from people worldwide. To help inform the public and increase prevention awareness, the Merck Manuals today released a list of waterborne illnesses that people tend to overlook in the United States, leaving them vulnerable to diseases caused by bacteria and microscopic parasites.

Originating in oceans, lakes, rivers or pools, these hidden dangers can cause illnesses that range from uncomfortable and inconvenient to life threatening. To shed light on these dangers, infectious disease specialist Dr. Larry Bush has identified five waterborne illnesses to be aware of when heading to the water and key steps to preventing them on

1. Giardiasis is an infection of the small intestine caused by the parasite Giardia, which lives in fresh water. The most common parasitic intestinal infection in the United States, Giardia can be present even in clean-appearing mountain streams, so hikers are at risk.

Symptoms typically appear one or two weeks after infection and include abdominal cramps, gas and watery diarrhea. If you think you have Giardiasis, make an appointment with a doctor, who will likely ask for a stool sample. Treatment typically involves a course of antiparasitic drugs.

2. Shigellosis is an infection caused by the bacteria Shigella. An estimated 500,000 people in the U.S. develop the infection every year from water contaminated with human waste and inadequately chlorinated pools. Individuals don't have to ingest very much water contaminated with Shigella to become infected.

Symptoms include fever and diarrhea along with painful abdominal cramps. More severe infections may lead to dysentery – frequent bowel movements that may contain blood, mucus and pus. Treatment for Shigellosis includes fluids with salt and antibiotics for more severe cases.

3. Vibriosis is an infection caused by about a dozen Vibrio bacteria. Cholera is the most serious illness caused by the bacteria, but is not very common in the U.S. Noncholera Vibrio bacteria live in warm salt water or mixed salt and fresh water, like bays. Most noncholera Vibrio infections are intestinal infections caused by consuming inadequately cooked shellfish (especially oysters) harvested from contaminated waters. People can also develop Vibrio skin infections if they have an open cut and swim in contaminated water or cut themselves on a crustacean that harbors vibrio.

Vibriosis causes 80,000 illnesses each year in the U.S., according to the Centers for Disease Control. Symptoms include diarrhea, cramping, nausea, vomiting, fever and chills. Treatment is limited to drinking lots of water to replace lost fluids.

4. Escherichia coli (E. coli) is a group of bacteria that normally reside in the intestine of healthy people. However, some strains can cause infection, the most common being E. coli O157:H7. It can be contracted by swallowing inadequately chlorinated water that's been contaminated by the stool of infected individuals, for example in public pools.

Symptoms, primarily diarrhea and cramps, begin about three days after exposure. For E. coli 0157:H7, treatment is usually limited to administering fluids, and symptoms typically resolve within eight days.

5. Primary Amebic Meningoencephalitis (PAM) is an infection of the brain caused by the Naegleria fowleri amoeba. The amoeba lives in warm fresh water throughout the world and enters the brain by traveling up nerves from the nose. PAM is rare, only 138 people have died from it since 1962, according to the CDC, however it has recently made headlines in the U.S.

When the amoeba reaches the brain, it causes inflammation, tissue death and bleeding. Symptoms, which appear within one to two weeks, include a change in smell or taste, headache and stiff neck, sensitivity to light, nausea and vomiting. The infection moves fast, often causing death within 10 days.

Keys to prevention

The most effective prevention strategies go hand in hand with good overall health – make sure all vaccinations are up to date, drink only properly treated water and practice good personal hygiene. But there are more specific steps you can take before, during and after you go in the water to limit the risk.

Before you go in the water:

  • Check for official updates on the condition of the water and advisories warning people not to swim.
  • Inspect water for signs of bacteria or algae, which can cause skin irritation.
  • Avoid swimming in water where babies are wearing diapers or people have open cuts.
  • Shower to wash away any bacteria on you.

During your time in the water:

  • Avoid swimming with open cuts – even waterproof bandages do little to prevent bacteria entering a wound.
  • Swallow as little water as possible.
  • It's all right to open your eyes – eyes are mostly impervious to bacteria in the water.

After you get out of the water:

  • Take a shower immediately.
  • If you do contract an illness, alert the pool, township, park, etc. as quickly as possible with as many details as possible.

About The Merck Manuals and MSD Manuals

First published in 1899 as a small reference book for physicians and pharmacists, The Merck Manual grew in size and scope to become one of the world's most widely used comprehensive medical resources for professionals and consumers. As The Manual evolved, it continually expanded the reach and depth of its offerings to reflect the mission of providing the best medical information to a wide cross-section of users, including medical professionals and students, veterinarians and veterinary students, and consumers. In 2015, The Merck Manual and MSD Manual kicked off Global Medical Knowledge 2020, a program to make the best current medical information accessible by up to three billion professionals and patients around the world by 2020. For access to thousands of medical topics with images, videos and a constantly expanding set of resources, visit or and connect with us on social media: 

For Consumers in the U.S. and its territories: Twitter and FacebookFor Professionals in the U.S. and its territories: Twitter and Facebook

About Merck

Today's Merck is a global health care leader working to help the world be well. Merck is known as MSD outside the United States and Canada. Through our prescription medicines, vaccines, biologic therapies and animal health products, we work with customers and operate in more than 140 countries to deliver innovative health solutions. We also demonstrate our commitment to increasing access to health care through far-reaching policies, programs and partnerships. For more information, visit and connect with us on Twitter, Facebook, YouTube and LinkedIn.


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