Pathogenic human viruses in coastal waters

Abstract

This review addresses both historical and recent investigations into viral contamination of marine waters. With the relatively recent emergence of molecular biology-based assays, a number of investigations have shown that pathogenic viruses are prevalent in marine waters being impacted by sewage. Research has shown that this group of fecal-oral viral pathogens (enteroviruses, hepatitis A viruses, Norwalk viruses, reoviruses, adenoviruses, rotaviruses, etc.) can cause a broad range of asymptomatic to severe gastrointestinal, respiratory, and eye, nose, ear, and skin infections in people exposed through recreational use of the water. The viruses and the nucleic acid signature survive for an extended period in the marine environment. One of the primary concerns of public health officials is the relationship between the presence of pathogens and the recreational risk to human health in polluted marine environments. While a number of studies have attempted to address this issue, the relationship is still poorly understood. A contributing factor to our lack of progress in the field has been the lack of sensitive methods to detect the broad range of both bacterial and viral pathogens. The application of new and advanced molecular methods will continue to contribute to our current state of knowledge in this emerging and important field.

FIG. 1.

Real-time PCR. A TaqMan poliovirus standard curve generated by plotting threshold cycle (C_T) against the log of the virus concentration. The C_T occurs where the sequence detection software begins to detect an increase in signal due to the exponential growth of PCR amplicons. Standards are shown here in black, two natural-water samples seeded with poliovirus are shown in white. A 2-ml volume of a poliovirus Sabin type 1 cell culture was lysed by vigorous shaking, and extracellular DNA was digested with pancreatic DNase I. Viral particles were purified using a glycerol step gradient (136), stained with SYBR Gold, and directly counted by epifluorescence microscopy (104). The stock dilution contained 9.1 × 10³ viruses per μl. A 10-μl sample of the stock was purified and brought up in 70 μl of water. Four dilutions ranging from 1.3 × 10⁰ to 1.3 × 10³ were made using UV-treated 0.02-μm-pore-size-filtered deionized water to generate an RNA standard curve. RT-PCR on all standards was performed in triplicate. Two natural-water samples (white dots) were seeded with poliovirus and quantitated using this standard curve. The quantities of the two natural-water samples were 7.2 × 10⁰ and 1.7 × 10¹ viruses per μl.