New tools for the study and direct surveillance of viral pathogens in water

Abstract

Half a century ago scientists attempted the detection of poliovirus in water. Since then other enteric viruses responsible for gastroenteritis and hepatitis have replaced enteroviruses as the main target for detection. However, most viral outbreaks are restricted to norovirus and hepatitis A virus, making them the main targets in water. The inclusion of virus analysis in regulatory standards for viruses in water samples must overcome several shortcomings such as the technical difficulties and high costs of virus monitoring, the lack of harmonised and standardised assays and the challenge posed by the ever-changing nature of viruses. However, new tools are nowadays available for the study and direct surveillance of viral pathogens in water that may contribute to fulfil these requirements.

Figure 1

Possible routes of waterborne transmission of enteric viruses. Viruses are shed in extremely high numbers in the faeces and vomit of infected individuals. Pathogenic viruses are routinely introduced into the environment through the discharge of treated and untreated wastes, since current treatment practices are unable to provide virus-free wastewater effluents. In consequence viral pathogens contaminate the marine environment (a), fresh water (b) and ground water (c). Mankind is exposed to enteric viruses through various routes: shellfish grown in polluted waters, contaminated drinking water and food crops grown in land irrigated with sewage contaminated water and/or fertilised with sewage. Surface and ground waters are employed for public consumption (e) and have been implicated in waterborne outbreaks of gastroenteritis and hepatitis. Foods susceptible to be contaminated at the pre-harvest stage such as bivalve molluscs (d), particularly oysters, clams and mussels; salad crops (f), as lettuce, green onions and other greens; and soft fruits (g), such as raspberries and strawberries have also been implicated in outbreaks of viral diseases.