Are Waterborne Diseases the Silent Killer of Summertime?

When the summer months roll around, we all love to have a dip in a swimming pool. It’s relaxing, fun, and a nice way to spend a few hours. But did you know that it can make you incredibly unwell? Waterborne diseases are far more common than you might imagine.

An exhaustive 2012 study by the CDC found that these numerous waterborne diseases are resilient even when faced with chlorine, and often capable of hospitalizing otherwise healthy adults. The risks are even greater for young children, the elderly, or the immune compromised. These diseases – known as recreational water illness (RWI) – can range from mild inconveniences to serious medical situations.

Here are some of the most dangerous waterborne diseases, according to the CDC.


Cryptosporidium is a microscopic parasite that continues to be the most common cause of recreational waterborne outbreaks. Half of the recreational water-associated outbreaks reported to the CDC during a 2011-2012 study were caused by Cryptosporidium. Cryptosporidium is an extremely chlorine-resistant parasite that can survive in water at CDC-recommended chlorine levels (1–3 mg/L) and pH (7.2–7.8) for longer than a week, so it’s very difficult to protect against.

Cryptosporidiosis (Crypto) is a parasitic disease caused by Cryptosporidium. Symptoms include watery diarrhea, stomach cramps or pain, dehydration, nausea, vomiting, fever, and rapid weight loss. These symptoms can last for 1-2 weeks or sometimes up to 30 days. Cryptosporidium can be released in a bowel movement from an infected human or from animal faeces, so regular cleaning of the pool – and perhaps keeping your pets out of the water – is the best way to prevent against this disease.


One of the most common waterborne diseases picked up in recreational swimming pools is good old-fashioned diarrhea. Diarrhea illnesses are caused by germs known as Crypto (see above) that are mainly spread through transmissions. Swimmers who have diarrhea, or have had it recently, are in danger of spreading diarrhea when they use pools because tiny amounts of fecal matter rinse off their bodies and stay in the water. If another swimmer swallows that water, they are at risk of developing diarrhea and spending the next few days with loose, watery stools, abdominal cramps, abdominal pain, fever, blood in the stool, bloating and nausea.


Schistosomiasis, also known as Bilharzia, is a disease caused by parasitic worms released by snails. This type of infection occurs when a person’s skin comes into contact with contaminated freshwater (e.g. rivers or outdoor swimming pools) where certain types of snails that carry the parasitic worms called schistosomes are gestating in.

Pool water becomes contaminated by Schistosoma eggs when infected people urinate or defecate in the water, which happens a lot more than what you’d expect. The eggs hatch in the temperate water and if certain types of freshwater snails are present in or around the water, these parasites develop and multiply inside the snails.

The initial symptoms include a rash or itchy patches on your skin. This is followed by fever, chills, cough, and muscle aches, within 1-2 months of initial infection. However, these are rare and most people don’t display symptoms at this early phase of infection.

When adult worms are present, the eggs that are produced travel to the intestine, liver, or bladder, causing serious inflammation or scarring. After years of infection, the parasite can end up permanently damaging the infected organs which can cause serious health issues. This can be avoided by keeping your pool water on rolling boil before use and regularly changing your water.

Be Safe This Summer

This is a brief overview of the many illnesses that can be picked up in your backyard or local municipal pool so it’s essential to be very careful at this time of year. The best way to prevent against waterborne illnesses is by regularly monitoring your own pool and changing the water, keeping your animals out of the pool, and washing before and after you get into the pool. Once you’re regularly maintaining your pool in this manner, you can focus on catching some sun instead of a diarrhea!