The Centers for Disease Control and Prevention (CDC) announced that one-third of swimming-related illnesses from 2000 - 2014 could be traced back to contaminants in treated hotel pools or hot tubs. These illnesses are on the rise.
The majority of the infections were caused by the Cryptosporidium (Crypto) parasite, or Pseudomonas and Legionella bacteria. All of them are resilient microbes; Crypto can live in treated pools, and the bacteria can resist the disinfectants used in hot tubs.
One group of people that can make a difference in preventing these infections are parents of young children. Kids that contaminate water with feces are a main source of Crypto; if another swimmer swallows even a mouthful of that contaminated water, they may be sick for weeks.
Source: CDC