The quality of bathing water in the European Union has been regulated since 1976 by the Bathing Water Directive (76/160/EEC). This directive was revised in 2006 (rBWD/CEU, 2006). According to Article 14 of this revised version, an integrated European framework was set up to determine both the frequency and the occurrence of two human enteric viruses: adenoviruses and noroviruses. Adenoviruses have been selected because of their near-universal shedding and environmental survival. Noroviruses have been selected due to their prevalence regarding gastroenteritis. Enteric viruses in water may originate from discharges of raw or treated water. They can contaminate bathing water after being discharged into surface water that is used for recreational water activities.
Surveillance in recreational water of such viruses required a global survey: 15 laboratories located in nine countries carried out a sampling campaign during the EU bathing season in 2006. This work was performed within a European project called VIROBATHE, which was funded under the sixth Framework Programme (FP6). VIROBATHE aimed to devise a robust, rapid and cost-efficient routine method for tracking the presence of enteric viruses in recreational water. Both fresh water and marine water were studied. VIROCLIME, an on-going FP 7 – ENV EC funded project, makes use of these outcomes for modelling the effects of climate on the variation in viral fluxes.
The methodology which has been developed within VIROBATHE for analysing enteric viruses was composed of two main phases: the concentration step and the detection step.
Concentration of freshwater samples was performed via glass wool filtration whereas concentration of marine water samples was carried out via membrane filtration. An amount of 10 g glass wool was compressed and embedded in a polystyrene column to obtain a 6-8 cm filtrating device. After different leaching and washing steps, the resultant protein floc containing the virus was centrifuged and stored at – 20°C. Concerning the marine water samples, these were processed via nitrocellulose membranes, elution and organic flocculation. These two physical filtrating procedures allowed extracting the Nucleic Acid (NA) from the concentrates for a further detection technique based on molecular detection.
Detection of enteric viruses was thereafter achieved by using RT-PCR. This stands for Reverse Transcriptase Polymerase Reaction Chain. RT-PCR aims to transcribe RNA into its DNA complement. This DNA is then amplified using PCR.
In practice, every laboratory selected two sampling sites (main site and second site) for the study. A total of 24 sites were sampled and analysed from the end of May to the beginning of November 2006, thereby including the bathing season in all member states. From the overall survey data, 553 out of 1410 samples (i.e. roughly 40 %) were positive for one or more target viruses. This result means that almost 40% of bathing water represents a public health risk. It has also been established that freshwater sites showed a higher frequency of virus-positive samples than marine sites. Moreover, it has been shown that adenoviruses are more prevalent than noroviruses in both marine and freshwater samples. Therefore, adenoviruses appear to be a promising
in situ bio sensing indicator for assessing the quality of bathing water.
Surveillance of adenoviruses and noroviruses in European recreational waters.
Water Research 45 (2011) 1025-1038