title: Why are river recreationalists most at risk for development of waterborne infectious diseases: how can clinicians improve surveillance? A national problem.
mesh_terms: D000818:Animals; D003457:Cryptosporidiosis / Q000453:epidemiology* / Q000209:etiology; D016785:Cryptosporidium parvum / Q000302:isolation & purification; D004781:Environmental Exposure / Q000009:adverse effects*; D005767:Gastrointestinal Diseases / Q000382:microbiology* / Q000469:parasitology; D005872:Giardia / Q000302:isolation & purification; D006801:Humans; D011998:Recreation; D012722:Sewage / Q000469:parasitology*; D014481:United States / Q000453:epidemiology; D014871:Water Microbiology; D014873:Water Pollutants / Q000009:adverse effects* / Q000032:analysis
chemical_list: D012722:Sewage; D014873:Water Pollutants