Pool germs: how to stay safe when swimming

On scorching summer days, there are few pleasures as refreshing as a swim in a pool. Yet, have you ever considered whether the water is truly as clean as its clear blue appearance suggests?

As an immunologist and infectious-disease specialist, I research how germs circulate in public settings and ways to stop their transmission. I also teach a module entitled "The Infections of Leisure", in which we examine the hazards linked to leisure activities and the precautions people can take, without making students fearful of germs.

Swimming, particularly in public pools and water parks, carries a distinct range of risks, spanning minor skin irritation to gastrointestinal illness. At the same time, it offers abundant physical, social and mental-health benefits.

Armed with a little knowledge and some sensible awareness, you can enjoy the water without becoming preoccupied with what may be beneath its surface.

The truth about pool germs

Summer headlines and social-media posts frequently draw attention to the “ick factor” of shared swimming facilities. Those worries are not entirely unfounded.

The encouraging news is that chlorine, which is commonly used in pools, kills many disease-causing organisms effectively. The less encouraging part is that it does not act immediately - and it cannot destroy every germ.

Each summer, the Centers for Disease Control and Prevention (CDC) publishes warnings about outbreaks of illness associated with exposure to germs in public pools and water parks.

A 2023 CDC report identified more than 200 pool-related outbreaks across the US between 2015 and 2019, affecting over 3,600 people. These incidents involved skin infections, respiratory problems, ear infections and gastrointestinal upset. Although many infections cause only mild symptoms, some may be severe.

Pool germs and disinfectants

Some pathogens can remain in the water for minutes or even days, including in a pool that has been correctly chlorinated.

Among the most frequent offenders is Cryptosporidium, a microscopic germ responsible for watery diarrhoea. This single-celled parasite has a resilient outer coating, enabling it to withstand chlorinated water for as long as 10 days. It is transmitted when faecal material - commonly from a person with diarrhoea - gets into the water and is then swallowed by another swimmer. A minuscule, invisible amount can be enough to infect dozens of people.

Another widespread germ is Pseudomonas aeruginosa, a bacterium behind hot-tub rash and swimmer’s ear. Viruses including norovirus and adenovirus may also persist in pool water and make swimmers ill.

People bring numerous bodily residues into pool water, such as sweat, urine, oils and shed skin cells. In particular, sweat and urine react with chlorine, producing chemical compounds known as chloramines that can create health concerns.

These compounds cause the familiar powerful chlorine odour. A clean pool should not have an intense chlorine smell - or any other odour, for that matter. It is a widespread misconception that a strong chlorine scent signals a clean pool. In reality, it can be a warning sign of the reverse: the water may be contaminated and best avoided.

Staying safe at a public pool

Straightforward steps taken by pool operators and swimmers can reduce most pool-related hazards. While most illnesses linked to pools will not be fatal, nobody wants to spend a holiday - or a glorious week of summer weather - confined to the bathroom.

These 10 suggestions can help you steer clear of germs at the pool:

• Shower before you swim. Rinsing for at least one minute removes most body dirt and oils, which can otherwise make chlorine less effective.
• Stay out of the pool when you are unwell, particularly if you have diarrhoea or an open wound. Germs can spread rapidly through water.
• Keep water out of your mouth where possible, reducing the chance of swallowing germs.
• Do not swim when you have diarrhoea, helping to limit the spread of germs.
• If you have been diagnosed with cryptosporidiosis, commonly known as “crypto”, wait two weeks after your diarrhoea has ended before going back into a pool.
• Take regular toilet breaks. Routine visits to the toilet, for both children and adults, reduce the likelihood of accidents in the water.
• Check nappies every hour, and change them away from the pool to avoid faecal contamination.
• Dry your ears carefully after swimming to reduce the risk of swimmer’s ear.
• Avoid swimming with an open wound - or, at minimum, ensure it is fully sealed with a waterproof dressing to protect yourself and other swimmers.
• Shower after swimming to wash germs from your skin.

Lisa Cuchara, Professor of Biomedical Sciences, Quinnipiac University

This article is republished from The Conversation under a Creative Commons licence. Read the original article.