What You Need to Know Before Swimming in a Public Pool or Hot Tub

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Story at-a-glance -

  • Hotel pools and hot tubs have become notorious for spreading a diarrheal disease caused by microscopic parasites known as Cryptosporidium, dubbed “Crypto”
  • Cramps, nausea, vomiting, fever and dehydration are all symptoms of Crypto, usually caused by swallowing pool water containing Crypto bacteria
  • Between 2009 and 2010 there were 24 outbreaks; between 2011 and 2012, there were 90, resulting from swimming in recreational waters such as pools; half of the bacterial culprits found in the water were Crypto
  • Crypto parasites can live in the intestines of both humans and animals, be passed through their feces, and can remain in peoples’ small intestines for as long as two weeks, causing symptoms to reappear off and on for days
  • One little-known but protective step you can take before you enter the water is to check out inspection scores recorded by the health department that may be posted near the pool. You can also get test strips to test it yourself

By Dr. Mercola

For many, swimming is a favorite pastime of summer, especially while on vacation. However, as noted by CNN,1 what may be lurking in your hotel pool and/or hot tub might literally turn your stomach. In this case, it's a diarrheal disease caused by microscopic parasites, giving teeth to the phrase "What you can't see can hurt you."

Waterborne Parasite Infections Are on the Rise

Infectious disease specialist Jaime Zapata from University Hospital in San Antonio explains the most common symptoms telling you something is definitely wrong include "… cramps, nausea, vomiting, fever, dehydration, so be aware that if you go to the swimming pool, shower after."

That's good advice, according to CNN's Susan Scutti, who notes that so far this year, while that particular hospital hasn't yet seen a case of Cryptosporidium, often dubbed "Crypto," (not to be confused with the currency) the Centers for Disease Control and Prevention (CDC) is worried, and it's no wonder:

"Hotels set the stage for nearly a third of all disease outbreaks in the United States linked to chlorinated or treated water — such as pools and hot tubs — between 2000 and 2014, according to a new government report. During that 15-year period, a total of 493 outbreaks linked to treated recreational water were reported in 46 states and Puerto Rico, the report indicates."2

The CDC also breaks down numbers for the years between 2009-2010 compared to 2011-2012: There were 24 outbreaks and 90 outbreaks, respectively, from swimming in recreational waters such as pools and other bodies of water in the U.S., and half of the culprits found in pool water were Crypto.

Outbreaks are described as occurring when two or more people who become ill are linked by location and time frame to the same body of water. The average time before someone infected by the parasite becomes sick is seven days, but it can range between two and 10. Serious cases can also infect your respiratory tract.

Statistics and Other Data on Crypto

According to the CDC's Morbidity and Mortality Weekly Report,3,4,5 between 2000 and 2014, a total of 493 disease outbreaks were sourced to public pools and hot tubs — 32 percent of which were traced back to hotels.6 In all, these waterborne outbreaks led to 27,219 illnesses and eight deaths.

Crypto was the primary culprit in these cases, accounting for nearly 60 percent of pool-related outbreaks. Six of the eight deaths and 16 percent of the illnesses were associated with bacterial Legionella, a sometimes-fatal pneumonia, which you may remember was the cause of a massive outbreak in 1976 called Legionnaires' disease.

Pontiac fever, which causes mild flu symptoms, is another bacterial disease from a bacteria implicated in those cases, as is folliculitis ("hot tub rash") and otitis externa ("swimmers' ear"), from a bacteria known as Pseudomonas. Legionella and Pseudomonas can both tolerate disinfectants and retain their ability to make people sick for longer than you would think. About half of the outbreaks were between June and August, with a smaller peak in March. The CDC also states:

"Chlorine inactivates most pathogens within minutes although extremely chlorine-tolerant Cryptosporidium can survive for (more than) seven days (and) is transmitted when a diarrheal incident (i.e., a high-risk Cryptosporidium contamination event) occurs in the water and the contaminated water is ingested.

The parasite's extreme chlorine tolerance enables it to persist in water, cause outbreaks that sicken thousands, and spread to multiple recreational water venues and other settings (e.g., child care settings)."7

Crypto has made a name for itself in the U.S over the last two decades as one of the most common causes of waterborne disease, and not just pools and hot tubs but drinking water as well. It should be noted that the parasite can be found in every area of the U.S. and throughout the world. Needless to say, washing your hands thoroughly and often becomes more urgent once you're aware that such diseases are caused by a parasite that's basically spread through exposure to feces.

It spreads when you touch your mouth with contaminated hands. Contamination comes with touching objects that perhaps others touched with infected hands, from stair railings to elevator buttons to doorknobs to baby toys. The CDC also notes that you're not always able to tell by looking at something if it's been in contact with fecal matter.

How to Combat Crypto

You might think that hotel pools would have chlorine and filters that would take care of the germs that spawn such outbreaks, and you'd be right, but the worrisome part is that both are ineffective for handling Cryptosporidiosis. Crypto parasites can live in the intestines of both humans and animals and be passed in the feces of an infected person or animal.8

Parasites can remain in peoples' small intestines for as long as two weeks, causing symptoms to reappear off and on for days before the infected person fully recovers. As Water Quality & Health Council notes:9

"Although chlorine destroys most disease-causing germs in treated recreational waters within minutes, Crypto presents a unique challenge. The issue is that in its infectious life stage, the parasite is protected from chemical disinfectants by a hard outer shell, known as an 'oocyst.' Thanks to that resistant shell, Crypto can survive for days in a properly chlorinated pool."

"Really, the first line of defense is that if somebody has diarrhea or is sick, don't allow them in your pool," says CNN newscaster Ursula Pari. While many community pools have such strict guidelines that they'll shut down if they suspect contamination, much of the weight of responsibility falls on the parents of small children. Zapata notes that if you have younger than 2-year-old children with you at the pool, they should be taken to the bathroom often.

"Be aware that that child could do something in the swimming pool," he says. While rule No. 1 would be "Don't drink the water you swim in," it's very difficult to get that across to babies, toddlers and other young children. Not using the pool as a toilet is hard to get across to them, too.

According to Michele Hlavsa, lead author of the report and chief of the CDC's healthy swimming program, most healthy people recover from Crypto contamination without treatment, but if diarrhea doesn't go away on its own within three days, you should call your doctor. Other commonsense recommendations include:

Teach your children not to swallow water when swimming

Take your children on bathroom breaks every hour, and check diapers in the designated diaper-changing area (not next to the pool)

Keep your children out of the pool if they have diarrhea, or have had a bout of diarrhea in the past two weeks

Avoid using pool toys that might encourage your child to get water in their mouth, such as cups and buckets

If you know you've had a parasitic infection, wait at least two weeks after the diarrhea stops before getting into the water

Shower before and after entering the pool or hot tub

Never urinate (or defecate) in the water

Don't Drink the Water but Also Check It First

Another little-known but protective step you can take before you enter the water: Check out the inspection scores that may be posted by the health department, near the pool. They're similar to the way restaurants post the scores of their kitchens' food safety and sanitation practices. Just keep in mind that while public pools may be subject to tests, private pools usually aren't. Another option that may ease your mind is to check the water yourself. As CNN notes:

"After all, hotels, community pools and recreational hot spots probably are not checking their water every day, and pool chemistry changes all the time. Pool supply stores and big box stores sell inexpensive test strips, which test for chlorine and pH. If levels are unsafe … don't swim."10

Although you can get test strips inexpensively at pool supply and big box stores, free, over-the-counter pool and hot tub/spa test strips are made available through the Water Quality & Health Council (WQHC) on its Healthy Pools page.11 Here's one reason why you may want to take it seriously:

"Why worry? These survey findings are especially concerning in light of a 2016 CDC report that found nearly 8 in 10 routine inspections of public pools turned up at least one violation of health and safety rules, and 1 in 8 found problems so serious the pool had to be closed immediately."12

According to Chris Wiant, chair of the WQHC, it's not just chlorine that makes peoples' eyes red, it's contaminants like sweat, dirt and pee from other swimmers' bodies mixed with the chlorine that causes bloodshot eyes. You'd like for everyone to adhere to the rules, but as far as it depends on you, Wiant says, "Protect yourself and loved ones by showering before going in the pool, and don't pee in the water."

A Few More Disconcerting Statistics

One of the basic rules for pool etiquette is to shower before getting into the pool. Nobody monitors this, obviously; it's more like relying on the honor system. As you can imagine, most people think if there's a problem it's caused by someone else — it couldn't be them.

Keep in mind that a lot of kids wonder why there's a rule in the first place; they figure that if they needed a shower, wouldn't a swim in the pool do the job for them? Thinking in terms of how diseases like Crypto take place isn't one they're able to connect all the dots on. But that's kids for you. Unfortunately, statistics say adults are just as bad, and maybe worse. According to a WQHC survey conducted in 2017:

  • 25 percent of adults would swim within 30 minutes of having diarrhea
  • 52 percent routinely skip the shower before swimming in a pool
  • An unbelievable 60 percent admit to swallowing the water while they're swimming
  • 72 percent of adults are not aware there's a disease known as Crypto; that it's caused by a parasite and that it can spread in pool water
  • 84 percent of adults don't realize that agents like chlorine, even used at levels recommended by the CDC, will not eradicate Crypto in swimming pools

Science News contends you may as well face the fact that if you swim in a pool, whether it's private, at a hotel or used by a whole community, there's going to be pee in it. To some degree there will likely be fecal matter as well, they say, along with a fair amount of human sweat with some dead skin cells thrown in. They don't stop there:

"Swimming pools are basically huge blue toilet bowls. We've all peed in them — be honest — and a new study is stirring up our guilt by showing that urinating in a chlorinated pool creates a toxic chemical called cyanogen chloride. Cyanogen chloride forms when chlorine from the pool reacts with nitrogen in urine. It acts like tear gas, roughing up the eyes, nose and lungs, and it's classified as an agent of chemical warfare."13

The study14 notes that "uric acid introduction to pools is … a voluntary action for most swimmers;" "these findings indicate important benefits to pool water … that could result from improved hygiene habits on the part of swimmers."

How to Kill Crypto in Drinking Water

Crypto, as stated, is notorious for being impervious to chlorine. The CDC's advice for people wanting to kill or inactivate crypto in drinking water entails bringing your water to a rolling boil for one minute. At elevations above 6,500 feet, boil for three minutes.

Water should then be allowed to cool and stored in a clean, sanitized container with a tight cover and refrigerated. When using water from a stream on a camping trip, for instance, a point-of-use filter is a good thing to have. Keep in mind, however, that not all home-use water filters eliminate cryptosporidium. To protect against Crypto, the CDC recommends using:15

  • Reverse osmosis
  • Absolute pore size of 1 micron or smaller
  • Tested and certified to NSF/ANSI Standard 53 or NSF/ANSI Standard 58 for cyst removal
  • Tested and certified to NSF/ANSI Standard 53 or NSF/ANSI Standard 58 for cyst reduction

ANSI, the American National Standards Institute, is the official certifying agency in the U.S., but the NSF (National Sanitation Foundation, or NSF International), is not a government agency.16 The U.S. Environmental Protection Agency, as well as all U.S. states, the Standards Council of Canada (SCC), Health Canada and all of Canada's provinces rely on ANSI and SCC to determine the standards accepted for third party product certification. Other alternative water disinfection strategies recommended by the CDC include:17

  • Systems utilizing ultraviolet light
  • Ozone

Safer Disinfection Methods for Your Private Pool or Hot Tub

While you may feel safe in your private pool or hot tub, parasitic infestations can occur here as well, especially if children are using your pool and/or standard safety recommendations are not heeded, such as showering before entering. Avoid hyperchlorinating — zapping your water with high doses of chlorine — as this can produce extremely toxic gases far worse than a parasitic infection.

Between 2008 and 2015, there were 156 incidents in California alone where people were sickened by toxic chlorine gas inhalation at public water venues.18,19

An example of such an emergency occurred when about 34 of the 50 people in an outdoor pool in Contra Costa County, California, began experiencing eye irritation, coughing or vomiting. A chemical controller malfunction had allowed the release of sodium hypochlorite, which reacted with muriatic acid and the release of toxic chlorine gas. According to the CDC, more than 4,800 people throughout the U.S. visited emergency rooms for similar chemical-related health issues in 2012.20

Symptoms will depend on whether the chlorine poisoning involves the liquid or gas form, the amount, how long the exposure is and proximity to the source. Chlorine gas was used as a chemical weapon during World War I. Exposure can cause skin redness, burning pain and blisters, blurred vision, a burning sensation in the nose, throat and eyes, difficulty breathing, coughing and/or fluid in the lungs.

Chlorine also reacts with bodily fluids causing hundreds of byproducts to be produced,21 including cyanogen chloride, which is highly toxic and volatile. Some of these disinfection byproducts are over 1,000 times more toxic than chlorine itself. In swimming pools, organic materials that can cross-react with chlorine to form toxic byproducts include hair, skin, dried sweat, dirt and urine. Lotions can also cause harmful chemical reactions.

A CDC report on chlorine notes,22 "When chlorine gas comes into contact with moist tissues such as the eyes, throat and lungs, an acid is produced that can damage these tissues." To prevent these kinds of exposures, pool chemicals must be properly handled and stored, and anyone working with them must be trained in pool chemical safety and the proper operation and maintenance of the equipment. This applies at home as well.

On a positive note, you have more options and control of your private pool or hot tub. For example, saltwater pools23 are a healthier option. There are also ozone and ultraviolet light sanitizers24 you can use. Ozone and UV systems can reduce the need for chlorine by 50 to 90 percent, according to a report in Aqua Magazine.25

The Takeaway: Forewarned Is Forearmed

The best conclusion you can come to is that "forewarned is forearmed." Understand that public access may bring with it more than you bargained for. As for yourself, take the recommendations seriously:

  1. If you have diarrhea or have had it in the previous two weeks, stay out of pools and hot tubs and any other body of water.
  2. Shower before you get into the pool; even one minute will remove most anything from your body.
  3. Don't swallow the water. Ever.
  4. This one may be the most difficult, but if you happen to witness, or indeed experience a "diarrhea incident" yourself, report it to the pool staff immediately.

If there's good news, it's this: People with healthy immune systems are less likely to get sick from Crypto. So besides washing your hands and adhering to the previous list of recommendations, keeping your immune system in tip-top shape might be better for your health than you realized.

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