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Optimizing virus detection for the Dutch Drinking-water Directive

Optimalisatie van virusdetectie ten behoeve van het Nederlandse Waterleidingbesluit


Pathogenic viruses are detected more regularly and in higher concentrations than previously through the introduction of clinical virological methods into water sampling.Compliance of drinking-water quality with the Dutch Drinking-water Directive has been achieved when no more than one in every 10,000 persons per year is infected due to consumption of unboiled drinking water. To be able to assess this so-called 10-4 infection risk, accurate data are required on the numbers of viruses in the water used for producing drinking water. Various factors can influence the detection of viruses in water, such as the recoveries the method supports and the way viruses are quantified. It is also important to know if the method detects solely infectious viruses or includes non-infectious viruses as well. Virus concentrations in water can be more accurately determined by optimizing the current detection methods. A detailed study on the above mentioned aspects of virus detection was performed. Molecular methods derived from clinical virology were applied here for virus detection in water, resulting in 25 to 1000 times higher virus concentrations than were measured previously. Using these molecular methods both infectious and non-infectious viruses are detected. Because only infectious viruses can cause an infection and possibly illness in humans, the concentration of infectious virus should be determined to assess the infection risk. Infectious enteroviruses have been determined by classical cell culture methods for years. By combining cell culture and molecular methods, infectious rota- and adenoviruses can also currently be measured. Of the viruses detected by molecular methods, only one of 50 to 5000 virus particles appeared to be infectious, depending on the virus and the water sample. The improvements in virus detection in water will lead to a more precise estimation of the virus concentrations in that water, which will consequently improve the assessment of the 10-4 infection risk.

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