Inadequately Treated Wastewater as a Source of Human Enteric Viruses in the Environment

A Water and Marine Sustainability Month Feature Article

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Wastewater effluent in Peru. Public domain image by Nigel Wylie

Anthony I. Okoh, Thulani Sibanda  and Siyabulela S. Gusha (Applied and Environmental Microbiology Research Group (AEMREG), Department of Biochemistry and Microbiology, University of Fort Hare) have published a paper titled “Inadequately Treated Wastewater as a Source of Human Enteric Viruses in the Environment”, the summary of which reads:

Human enteric viruses are causative agents in both developed and developing countries of many non-bacterial gastrointestinal tract infections, respiratory tract infections, conjunctivitis, hepatitis and other more serious infections with high morbidity and mortality in immunocompromised individuals such as meningitis, encephalitis and paralysis. Human enteric viruses infect and replicate in the gastrointestinal tract of their hosts and are released in large quantities in the stools of infected individuals. The discharge of inadequately treated sewage effluents is the most common source of enteric viral pathogens in aquatic environments. Due to the lack of correlation between the inactivation rates of bacterial indicators and viral pathogens, human adenoviruses have been proposed as a suitable index for the effective indication of viral contaminants in aquatic environments. This paper reviews the major genera of pathogenic human enteric viruses, their pathogenicity and epidemiology, as well as the role of wastewater effluents in their transmission.

The introduction to this work reads:

Human enteric viruses are obligate parasites of man that infect and replicate in the gastrointestinal tract of their hosts. Patients suffering from viral gastroenteritis or viral hepatitis may excrete about 105 to 1011 virus particles per gram of stool, comprising various genera such as adenoviruses, astroviruses, noroviruses, Hepatitis E virus, parvoviruses, enteroviruses (Coxsackie viruses, echoviruses and polioviruses), Hepatitis A virus, and the rotaviruses. Consequently virus concentrations in raw water receiving fecal matter are often high; although viruses cannot reproduce in water they are still capable of causing diseases when ingested, even at low doses.

Human enteric viruses are causative agents of many non-bacterial gastrointestinal tract infections, respiratory infections, conjunctivitis, hepatitis and other serious infections such as meningitis, encephalitis and paralysis. These are common in immunocompromised individuals with high morbidity and mortality attributable to these infections in both developed and developing countries. Most cases of enteric virus infections have particularly been observed to originate from contaminated drinking water sources, recreational waters and foods contaminated by sewage and sewage effluents waters.

Wastewater treatment processes such as the activated sludge process, oxidation ponds, activated carbon treatment, filtration, and lime coagulation and chlorination only eliminate between 50% and 90% of viruses present in wastewater, allowing for a significant viral load to be released in effluent discharge. Due to their stability and persistence, enteric viruses subsequently become pollutants in environmental waters resulting in human exposure through pollution of drinking water sources and recreational waters, as well as foods. The performance of wastewater treatment systems is at present monitored largely by the use of bacterial indicator organisms. Considering that infectious viruses have been isolated from aquatic environments meeting bacterial indicator standards, in some instances in connection with virus related outbreaks, the use of bacterial indicators has thus been considered an insufficient tool to monitor wastewater quality because bacterial and viral contaminations are not necessarily associated and linked with each other. This paper reviews the major genera of pathogenic human enteric viruses, their pathogenicities and epidemiology, as well as the role of wastewater effluents in their transmission.

Read the full article in PDF format by clicking here.

Citation: Okoh, A.I.; Sibanda, T .; Gusha, S.S. Inadequately Treated Wastewater as a Source of Human Enteric Viruses in the Environment. Int. J. Environ. Res. Public Health 2010, 7, 2620-2637.

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  1. […] This post was mentioned on Twitter by Lloyd Y. Asato, Professor Paul. Professor Paul said: Health risks of inadequately treated wastewater in the #environment http://bit.ly/b1j2cW #water #health […]



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