Diseases Transmitted by Water

Most waterborne diseases are caused by microorganisms present in freshwater reservoirs, usually after contamination by human or animal feces. Transmission of the infectious agent through water may occur through contact with the skin during bathing, by ingestion or aspiration of germs present in the water.

Monsters in water
Monsters in water

The most common form of contamination is through ingestion, either by drinking contaminated water directly or by eating food washed with infected water.

In regions where there is no basic sanitation (lack of treated water or sewage), infectious diseases can occur due to the contamination of water from rivers, lakes, streams and in some cases even from the sea by human and animal waste . The most common mode of water contamination is through the discharge of untreated sewage.

Just to give you an idea, minimal amounts of feces, such as just one gram, can contain about 10 million viruses, 1 million bacteria, or up to 1000 parasites.

In addition to infections transmitted directly by the water, there are also other water - related diseases, such as infections caused by mosquitoes that breed in fresh standing water, including dengue, chikungunya fever and yellow fever. As these are not diseases transmitted directly by contaminated water, they will not be cited in this article.

Consumption of water contaminated by chemicals, such as lead, arsenic and fluoride, can also lead to disease.

In this text we will do a quick review on the major diseases caused by water contaminated with germs. If you want to know more details about the diseases mentioned in this text, use the provided links to access the specific articles about each one.

Hepatitis A

Hepatitis A is a viral infection transmitted by the fecal-oral route, ie the person must have contact with contaminated human feces to become contaminated.

Transmission of the hepatitis A virus can occur through contamination of food prepared by infected persons who do not wash their hands after evacuating or by contact with feces contaminated with water in places where there is no basic sanitation. Beaches, rivers and lakes that receive untreated sewage may have their waters contaminated with the hepatitis A virus.

Hepatitis A usually presents as a picture of diarrhea, associated with loss of appetite, nausea, vomiting, weakness, muscle pain, headache and fever. After a week arises jaundice, a classic symptom of acute hepatitis A, characterized by yellow skin and eyes.


Cholera is an infection caused by the bacterium Vibrio cholerae and is characterized by a severe picture of watery diarrhea, which can quickly lead to severe dehydration.

Cholera is also transmitted by the fecal-oral route, which can be acquired through water and contaminated food. The Vibrio cholerae, after being swallowed, settles in the intestine and starts to produce a toxin that attacks the intestinal cells, causing severe diarrhea.

Infectious diarrhea

In addition to cholera and hepatitis A, several other germs, including bacteria, viruses and parasites, can contaminate water and humans that come in contact with them. Just to name a few:

a) Bacteria:

b) Viruses:
  • Rotavirus
  • Norovirus (formerly called Norwalk virus)
  • Adenovirus
  • Sapovirus
  • Astrovirus
  • Enteric adenovirus
  • Polio
  • Hepatitis E

c) Parasites:
  • Giardia lamblia
  • Entameba histolytica
  • Trichuris trichiura
  • Isospora belli
  • Cryptosporidium parvum
  • Cyclospora cayetanensis


The main source of transmission of leptospirosis is the sewer rats. Infection can occur after consumption of fluids and food, but the main route is through direct skin contact with water contaminated by the urine of these rodents. The risk of transmission is high during floods when contaminated sewage water mixes with excess rainwater. The longer the contact of the skin with the water contaminated by the urine of the mouse, the greater the risk of contagion.

More than 75% of patients have a high fever with chills, headache and muscle pain. 50% present with nausea, vomiting and diarrhea. A typical finding of leptospirosis is the sharply reddish eyes.


Schistosomiasis, also known as watercress or snail disease, is an infection caused by the parasite Schistosoma, which lives in water contaminated by feces and populated by snail.

Schistosomiasis can be acquired through ingestion of contaminated water, but its main route is through the skin in people who bathe in water contaminated by the parasite.

Schistosomiasis can cause severe bowel and liver disease.

Otitis externa

Exposure from ear to water is a well-known risk factor for otitis externa (inflammation of the outermost ear). Otitis externa is also known as swimmer's otitis.

Excess moisture leads to maceration of the skin and breakage of the cerumen barrier, changing the microflora of the ear canal, which favors the growth of bacteria that cause otitis. Otitis can be caused by bacteria or fungi, and water with a high degree of contamination further increases the risk of ear injury. However, otitis can occur even in people who only go to swimming pools with adequate water treatment.


Legionellosis, also known as legionnaires' disease, is an infection caused by a bacterium called Legionella pneumophila. Legionellosis is a lung infection that is usually acquired through the inhalation of water particles contaminated with Legionella bacteria.

Legionellosis is not transmitted from person to person nor is it acquired through the consumption of contaminated water. To acquire Legionella you need to aspirate particles of contaminated water present in the environment.

Several types of water systems have been identified as potential sources of legionellosis. Among the most common are heating or cooling systems, central air conditioners, hot tubs, showers, high pressure water equipment, humidifiers, fountains, artificial fountains, nebulizers, steam saunas, etc. Any environment where there is vaporization or emission of water particles can be a source of contagion if the water is contaminated with the bacteria.

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