I have a cold, will this hurt the fish?

Bacteria can cross over, but few parasites can do so. Virii are another story--mutations aren't unheard of, but are certainly uncommon. Most transmissions revolve around open wounds in the water and ingestion. Mycobacterium and TB are the 2 most commonly discussed ones. Mycobacterium are everywhere, and seldom cause a problem, but the infections from them are very nasty and hard to cure. Infections of this sort are always the result of an open wound in the tank. While I have heard often that TB is transmissable, I have not heard of anyone who actually contracted it, so do not no the mechanism.

Overall, you're still safer playing in your aquarium than driving your car.
 
Sorry--phrased that wrong. They are one in the same-- Fish TB is Mycobacterium marinum , the aquatic equivalent of Mycobacterium tuberculosis , which is only found in humans. I have not heard of anyone contracting Fish TB from other than a tank, so don't know if there is a secondary transmission. Basically--I don't know if humans can transmit the Fish TB to others, or not. Human TB is easily transmissable.
 
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