Numerous viruses of human or animal origin can spread in the environment and infect people via water and food, mostly through ingestion and occasionally through skin contact. These viruses are released into the environment by various routes including water run-offs and aerosols. Furthermore, zoonotic viruses may infect humans exposed to contaminated surface waters. Foodstuffs of animal origin can be contaminated, and their consumption may cause human infection if the viruses are not inactivated during food processing. Molecular epidemiology and surveillance of environmental samples are necessary to elucidate the public health hazards associated with exposure to environmental viruses. Whereas monitoring of viral nucleic acids by PCR methods is relatively straightforward and well documented, detection of infectious virus particles is technically more demanding and not always possible (e.g. human norovirus or hepatitis E virus). The human pathogenic viruses that are most relevant in this context are nonenveloped and belong to the families of the Caliciviridae, Adenoviridae, Hepeviridae, Picornaviridae and Reoviridae. Sampling methods and strategies, first-choice detection methods and evaluation criteria are reviewed.

Cryptosporidium is a protozoan parasite that infects humans and various animal species. The environmental stability and the low infectious dose of Cryptosporidium facilitate its transmission by water and food. Discharge of untreated wastewater may result in waterborne or foodborne Cryptosporidium outbreaks, therefore a suitable treatment may prevent its dissemination. Most studies on the prevalence of Cryptosporidium oocysts in wastewater have reported a concentration range between 10 and 200 oocysts/L and a prevalence of 6 to 100%. Activated sludge has been found to be ineffective for the removal of Cryptosporidium oocysts. Stabilization ponds and constructed wetlands are efficient for the reduction of Cryptosporidium from wastewater, especially when the retention time is longer than 20 days at suitable sunlight and temperature. High rate filtration and chlorine disinfection are inefficient for the reduction of Cryptosporidium from effluents, whereas ultrafiltration and UV irradiation were found to be very efficient for the reduction of Cryptosporidium oocysts. Adequate tertiary treatment may result in high quality effluent with low risk of Cryptosporidium for unrestricted irrigation and other non-potable applications.

Survival and adsorption of pathogenic viruses in soil material can effect the extent of groundwater pollution by the application of wastewater effluents to soil. This study was conducted to determine the effect of soil composition and wastewater quality on the adsorption of pathogenic viruses (hepatitis A virus and poliovirus 1) and model bacteriophages onto soil. Moreover, the effect of temperature, soil composition and water quality on the die-off of pathogenic viruses and model bacteriophages was also studied. The effect of water quality on virus adsorption to soil was virus type dependant. Poliovirus 1 adsorption was the highest regardless of water type, whereas the poorest adsorption was observed for MS2 bacteriophage. Intermediate adsorption rates were observed for PRD-1 bacteriophage. No die-off was observed for any one of the studied viruses (HAV, poliol, MS2 and PRD-1) after 20 days incubation in soil saturated with secondary/tertiary treated wastewater at 10°C. At 23°C, the greatest die-off was observed for MS2 bacteriophage, which was incubated in soil saturated with secondary and tertiary treated effluents. Intermediate die-off was observed for poliovirus 1, whereas negligible die-off was observed for HAV and PRD-1 bacteriophages. This indicates that pathogenic viruses can survive for long period of time in soil at ambient temperatures. Our results indicate that polio 1 and MS2 bacteriophage can not be used as models for the persistence of pathogenic viruses such as HAV in soil. PRD-1 bacteriophage has been found to be more suitable than MS2 to predict the persistence of pathogenic viruses especially at ambient temperatures.

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