An outbreak of acute upper respiratory illness occurred among campers and counselors at a summer camp in North Carolina. Symptoms included: sore throat: cough; fever; headache; muscle ache; malaise; and conjunctivitis. Adenovirus type 3 was named as the cause of the illnesses, and swimming in the pond was associated with an increased risk of illness. Towel sharing was also associated with risk of illness. The camp had a one acre, manmade, pond with a maximum depth of ten feet. Well water was continously pumped into the pond. A chlorination system was in place to treat the water before it entered the pond. The pond water was turbid. The pond water showed evidence of coliforms, enterococcus, and staphylococcus; a pond water sample yielded adenovirus type 3; residual chlorine was not detectable. Viruses may survive better in turbid water and eventually settle into the cooler, pond sediment. Chlorine interacts with organic molecules in turbid water, thus inactivating the chlorine.