Swimming Pool Blog

Pool Pathogens: Bacteria in Pool & Spa Water

Pool Pathogens: Bacteria in Pool & Spa Water
by Rob Cox, March 18, 2013

Pool Pathogens and Bacteria ~ There's a Fungus Among Us!

swimming pool pathogensBacteria and viruses can easily find a home in swimming pool water. I'm not speaking about algae, which is not a pathogen (disease causing organism), but smaller, invisible creatures that can live in your pool or spa.

The CDC (Center for Disease Control) records thousands of cases of disease outbreak in pools and spas every year. They also monitor public pool health inspection reports. In a recent study, as many as 60% of public pools had violations.

Parasites, bacteria and viruses in swimming pools can lead to fever, vomiting and diarrhea in mild cases. More acute symptoms can lead to hospitalization and in rare cases can cause death.

Bacteria in My Pool? 

Water is a breeding ground for bacteria and can support viruses and parasites long enough for them to enter your body through absorption, inhalation, and/or ingestion. 

In the presence of chlorine, fungi is the most vulnerable, followed by bacteria. Viruses can take 10 times longer to be neutralized by chlorine, and protozoa is the most resistant, taking up to 100x longer than a fungus to be zapped by your pool chlorine.

Not surprisingly, the pathogens that take the longest time to kill also produce the most dangerous water borne illnesses.

How can Pool Water Become Contaminated? 

Fecal contamination is a leading cause of pathogens in pool water. Swimmers who don't wash their backsides before swimming or after using the bathroom (#2), are unknowingly rinsing off in the pool. It is estimated that the average waterpark facility has several pounds of fecal matter daily to deal with from their visitors. Yuck!

Accidental Fecal Release (AFR - a real term) is another method of entry. People with diarrhea should not use the pool for two weeks, to avoid an accidental release.

Aside from fecal matter, swimming pools can become contaminated by vomit, sweat, urine or saliva from an infected human or animal.

Parasitic infections can enter a swimming pool from food, particularly raw and uncooked proteins, such as eggs or fish, or can be brought into a pool from insects and wildlife that may fall into the pool.

Fill water can sometimes be the culprit, especially water that may have to travel far from the water treatment plant, or water from a contaminated well.

How can Swimmers Become Infected?

It depends on the pathogen. The most usual way is to swallow contaminated water, even small amounts that splash into your mouth and mix with your saliva. Some microbes can enter through the skin or through cuts on the skin. Eye, nose, ear and throat are the usual entry points.

How can Pool Water Contamination be Prevented? 

In most cases of micro organism outbreaks in swimming pools, nearly all in fact - the level of disinfectant is not high enough to combat the level of organisms. Filtering and circulation are also important to remove contaminants and distribute sanitizer. So, it's real simple really...

  1. Keep your chlorine level constant, at 1.0 ppm or higher.
  2. Shock your pool regularly to remove the unseen danger.
  3. Filter all of your pool water 1-2 times daily.
  4. Shower before you use the pool.
  5. No Dogs, No Babies. No Diarrhea. ;-)

Can Pool or Spa Water be Tested for Bacteria?

Well, I'm glad you asked! In fact, we have a bacteria test strip that you can use to test your pool or spa water for the presence of Coliform, E.Coli, Shigella, Pseudomonas and many other types of bacteria than can lead to RWI (Recreational Water Illness). Easy to use; returns results in just minutes.

Types of Bacteria found in Pools and Spas

E. coli - or Escherichia coli produces a toxin that damages the intestinal lining, resulting in stomach aches and diarrhea, from mild to severe. The virus lives in the intestinal tracts of animals and is excreted. It can come from domestic animals, farm animals or wild animals. E. coli responds as a unicellular organism. It can sense the presence or absence of chemicals and gases in its environment and move towards or away from them. It takes very little E.coli to infect, and can be drinking, bathing or swimming in contaminated water. E.coli bacteria can leach into wells in rural near large farms with poorly managed runoff.

Giardiasis - Also known as Giardia Enteritis, is a protozoan infection of the small intestine. It may bring on acute diarrhea and may lead to chronic intestinal disorders, malabsorption of fats and vitamins and weight loss. This disease in found more frequently in children than it is adults especially in areas where poor sanitation occurs. It is most often associated with drinking unfiltered surface waters or from shallow wells, swimming or wading in contaminated freshwater and contaminated recreational waters such as swimming pools and wading pools.
Cryptosporidiosis - Cryptosporidim Parvum, or "Crypto" for short is a parasite with a cryptic name. It infects not only humans, but many other animals including birds, fish, dogs, cats, and farm animals. The infections are frequently without symptoms, with helps spread the organism. Symptom include diarrhea, and also severe abdominal cramps. Fever, vomiting is also common. An interesting characteristic of this pathogen in pools is the appearance of oocysts which are highly resistant to chemical disinfectants. The oocysts are highly infectious, and in a moist environment, they may remain infectious for many weeks, even with proper sanitation.
Legionella - Legionnaires’ disease is caused by a bacterium known as Legionella Pneumophilia, and it is transmitted by inhaling small droplets of infected water suspended in the air. Legionella becomes more of a danger in hot water and small volumes of spas and hot tubs. To prevent it from showing up on your doorstep, keep your HVAC systems properly maintained and cleaned. Spas and pools can be carriers as well, but can be prevented with good water management and proper filtration. Legionella thrives in water or any moist and damp area. The symptoms are similar to the flu; fever, diarrhea and stomach upset.
Campylobacter jejuni - a slender, curved, and motile rod shaped bacteria. It is microaerophilic, which means it needs very little oxygen. It is a relatively fragile bacterium, and sensitive air, pH and temperature. It responds well to disinfectants. Surveys have shown that C.jejuni is the leading cause of bacterial diarrheal illness in the United States. Infection causes diarrhea and intestinal discomfor, along with fever and nausea. The illness can last 7-10 days, and relapses are not uncommon. This pool pathogen is easier to control than some of the others listed on this page.
Naegleria fowleri - Sometimes called the "Brain Eating Amoeba" is a free-floating amoeba-flagellate that invades the brain and the spinal cord and brain via the nasal passages. The organism may also cause infections of the eyes and skin rashes. This pathogen exists globally in the environment in both aquatic and soil habitats. Spas or hot tubs with naegleria have been found to be sources of eye infection, often confused with pink eye. Infections have most often been associated with swimming in lakes and ponds where infection is known, but few infections have been found in swimming pools. However, as a precaution, soft contact lens wearers should not wear lenses while swimming or using a hot tub, even if you don't go under water.

Pseudomonas - Pseudomonas aeruginosa is a bacterium which can cause disease in animals and humans. It is found in soil, water, skin flakes and most man-made environments throughout the world. In animals, this versatility enables the organism to infect damaged tissues or people with compromised immune systems. The symptoms of a pseudomonas infection are general inflammation or rash, and in severe cases, a blood infection can result. If infection occurs in critical body organs such as the lungs, the urinary tract, or the kidneys, results can be fatal. Pseudomonas aeruginosa is also known as hot tub folliculitis, as it is  common in public hot tubs and spas with poor sanitation practices. It can produce small red bumps on the skin, as well as intestinal discomfort and fever.

Shigella - bacteria that can infect the digestive tract and cause a wide range of symptoms, from diarrhea, cramps, vomiting, to more serious illnesses. Infections, called shigellosis, sometimes go away on their own; in others, antibiotics can shorten the course of the illness. Other symptoms of shigellosis include: high fever, loss of appetite,  and painful bowel movements. In very severe cases of shigellosis, a person may have convulsions (seizures).  Shigella is transmitted directly from uncleaner swimmers and may infect after ingestion of contaminated food or water. This pool pathogen may be acquired by swimming in contaminated surface waters or pools and spas.


Moral: Keep your pool and spa water balanced and sanitized, shock regularly, and washing well before using the pool can prevent RWI (Recreational Water Illness). To prevent contamination from an accidental release (AFR), persons with Diarrhea should not use the pool for a period of two weeks.