WRRCTR No.134 Survival, Dissemination, and Public Health Significance of Human Enteric Viruses in Ocean Waters off Oahu: Viability and Die-Off; Role and Effects of Antiviral Agent(s)

Abstract

The discharge of domestic sewage into the ocean waters off Oahu is a common practice. Since infectious enteric human viruses have been determined to be present in all sewages, viruses are also being discharged into the ocean environment. This study was undertaken to determine the fate, dissemination, and public health significance of sewage-borne viruses after they enter the ocean environment. Using an experimental, portable virus concentrator, indicator bacteria as well as human enteric viruses were consistently recovered from water samples taken from the surface sewage plume, the result of sewage discharge from the original ocean outfall pipe extending 129.8 m into Mamala Bay at a depth of 12.2 m. Recovery of sewage-borne bacteria and viruses decreased as the distance from the plume increased. However, viruses were recovered from a station as far away as 3 218 m east of the plume and within the vicinity of Ala Moana Beach. Significantly, viruses were occasionally recovered in the absence or negligible concentrations of coliform bacteria, indicating that the standard coliform test for water quality may be inadequate as an assessment for the presence of viruses. When the old sewage outfall pipe into Mamala Bay was diverted to the new outfall pipe which extends approximately 2 743 m from shore (exclusive of a 914 m long, multi-porthole diffuser) at a depth of 73.2 m, no surface plume was observed and viruses were only sporadically recovered from ocean waters above the discharge pipes (zone of mixing). Viruses were recovered from ocean waters near other ocean sewage outfalls, such as in Pearl Harbor, Kaneohe Bay, and Kailua Bay, as well as from boat marinas and a stream emptying into the ocean. Other studies showed that human enteric viruses can be expected to survive for 24 hr in the marine environment before they are actively destroyed. Moreover, evidence was obtained that microorganisms naturally present in all the marine waters off Oahu are responsible for the inactivation of human enteric viruses.