Expert Advice -- Do Germs Spread in a Swimming Pool?

Do germs spread in a pool? If others who are sick (i.e. have a cold) are swimming in the same pool as I, could I get sick from their germs?


Robert Steele


Bacteria and viruses are the most common causes of infection although other things such as fungi may cause problems as well. Each infectious agent has its own way of replicating and staying alive. Some are able to withstand being away from a human body for extended periods of time. The rotavirus which causes diarrhea may be deposited on diaper changing tables and toys and stay infectious for a couple of days. HIV, the virus which causes AIDS, on the other hand, is destroyed very shortly when left in the open air. Spores of certain fungi and the eggs of some parasites can withstand rather adverse conditions. Cryptosporidium which can cause gastrointestinal illness in most people and even death in those with AIDS was the culprit of widespread infection (estimated 403,000 people) in Milwaukee, Wisconsin when it got into the water supply despite reasonable water treatment.

Because there is such a variety of different organisms which may possibly come in contact with pools, elimination of as many of these as possible without causing toxic effects on humans is the common strategy. Keep in mind, the water itself is rather toxic to most organisms. So, just the fact that it is a pool will keep many bacteria and viruses from propagating. However, there are some bacteria that are actually water loving, and it is these organisms toward which most of our killing efforts are directed. The common strategy uses modification of the pH of the pool as well as chlorination or bromination of the water which is toxic to most of these infectious agents.

Despite best efforts, some infections may be transmitted through pool water. There have been reports of Giardia, a parasite which causes chronic diarrhea, being transmitted at a water slide park. Cryptosporidium has been reported to have been transmitted at one pool. And it is well known that a certain water-loving bacteria called Pseudomonas can cause inflammation of the skin, however, this is usually transmitted in hot tubs rather than swimming pools. In any of these cases, the infection is usually easily treatable.

Viruses are the things that cause the common cold, and these viruses are almost exclusively transmitted by direct contact with the secretions (primarily saliva). This is often done by hand shaking in adults (after having wiped the nose) or toys in infants. Many of these viruses are not able to survive in pool water. While it is theoretically possible that cold viruses which do survive in the pool water could be transmitted, it is highly unlikely due to the fact that such a large body of water makes for a rather dilute solution of viruses. It is much more likely that playing in the pool with the person who has the cold will allow for direct contact with saliva and nasal secretions and allow for much more efficient transmission of the virus.

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