Fish are very popular pets. It has been estimated that freshwater fish are owned by over 14 million people in the US, and saltwater fish are owned by approximately 800 000 people. Fish can be interesting, low maintenance pets, and the risks of disease transmission to people are low. However, low does not mean zero, and there are some diseases than can be spread from fish to people.

The most common (but still quite rare) disease that can be transmitted from fish to humans is infection with Mycobacterium marinum. This microorganism can be found in both freshwater and saltwater. It can cause skin infections, usually in areas where the skin is already broken, such as pre-existing scrapes and cuts, or skin that is damaged while cleaning an aquarium. Serious or long-term problems are rare in otherwise healthy people, but infection can be fatal in individuals with a weakened immune system.

Various other bacteria found on fish and in aquariums can cause infection in people as well. These are usually also "opportunistic infections" that tend to occur in people with weakened immune systems or infected wounds.

While fish are low risk pets, you can still minimize the risks that do exist by following a few simple precautions:

  • Wash your hands after contact with aquarium water or items in the aquarium. Gloves should be worn to prevent skin damage if you need to touch rough or sharp surfaces.
  • Do not clean an aquarium in the kitchen.
  • Do not dump aquarium water down the kitchen sink.
  • Prevent contact of aquarium water or contents with open wounds on your skin.
  • Keep aquariums covered. This helps keep other pets (e.g. cats) from drinking or playing in the water. (It also prevents escape attempts by the fish, which never end well!)