Enteroviruses (EVs), including poliovirus and nonpolio enteroviruses (i.e., coxsackieviruses, echoviruses, enteroviruses) are among the most common genera of the Picornaviridae family that infect humans and therefore are known to circulate widely in human populations throughout the world. New genera of the Picornaviridae family (i.e., Saffold cardiovirus [SAFV]) Cosavirus [common stool-associated picornavirus] Salivirus [stool Aichi-like virus]) have been identified in fecal specimens and wastewaters using conventional and highly-sensitive genomic sequencing technologies. In addition, members of the Echovirus genus originally known as echovirus 22 and 23 have been reclassified within the genus Parechovirus. Likewise, previous rhinovirus species have been reclassified within the Enterovirus genus. Enterovirus (EV) infections are a significant cause of morbidity and mortality throughout the world, primarily in infants and young children. Nevertheless, reliable worldwide estimates of EV-related mortality are not currently available.
Enteroviruses like most enteric viruses have evolved stability to adverse environmental conditions, including thermal stability, acid stability, resistant to radiation as well as to oxidants and proteolytic enzymes, which allow survival of these viruses in the environment and facilitate their transmission through multiple environmental routes (e.g., water, food, aerosols, and virus-contaminated inanimate objects or fomites). Human wastes, such as sewage and poorly treated effluents, urban stormwater and combined sewers overflows (CSO) are the primary source of enteroviruses released into aquatic and land environments that subsequently contaminate raw source waters for potable supply, bathing waters, shellfish waters, and waters used for irrigation of crops. Groundwater sources are also vulnerable to contamination with enteroviruses through different routes including direct injection of wastes through wells, percolation of sewage sprayed over the land, leaking or broken sewer lines, seepage from waste lagoons, infiltration of sewage-polluted surface streams, and septic tank effluents. The biophysical properties of enteroviruses (i.e., small-size, genome type and the non-enveloped capsid structure of the virion) play an important role on virus survival in the environment and on the physical removal and inactivation of virus particles through conventional wastewater treatment processes. Membrane bioreactor systems (MBRs) are becoming increasingly applied in developed regions as advanced wastewater treatment technologies to produce treated effluents of very high quality applicable to wastewater discharge and recycling solutions, including non-potable or indirect potable reuse. The distribution and persistence of enteroviruses in sewage-polluted waters may vary geographically depending on the epidemiological status of the population, population density, and the extent of sanitation coverage (i.e., wastewater treatment and wastewater disposal) which influence the viral load released into the environment. Recent estimates by the World Health Organization (WHO)/United Nations Children’s Fund (UNICEF) Joint Monitoring Programme for Water Supply and Sanitation indicate that despite significant progress on sanitation, in 2012, more than one third of the global population - some 2.5 billion people – do not use an improved sanitation facility, and of these 1 billion people still practice open defecation. Sewage represents a useful matrix to derive information on circulating enteroviruses in given populations and to describe the enterovirus epidemiology associated with human disease, also known as environmental surveillance.
Environmental poliovirus surveillance is a major goal of the WHO Global Poliovirus Eradication Initiative (GPEI) used to monitor pathways of poliovirus transmission of wild poliovirus and circulating vaccine-derived polioviruses (cVDPVs). A major effort to develop new, improved, and safer live polio vaccine is being promoted by the WHO, Rotary and the Bill & Melinda Gates Foundation. Human enteroviruses have been recovered worldwide from surface waters including coastal waters, rivers streams, and lakes, from ground waters, wastewaters and finished drinking water. Numerous methodological approaches have been recently developed for concentration of human enteric viruses from water and their isolation from the environment. Selection of an appropriate filtration method for the primary concentration of viruses is crucial to successful virus detection. However, an efficient method to recover all viruses has not been developed yet. Integrated cell culture and PCR (ICC-PCR) developed in the late 1980s is still applicable for detection and identification of a suite of infective viral pathogens recovered from environmental samples. The detection of enteroviruses in sources of drinking water and recreational water bodies has been broadly accepted as a marker of a possible failure of the sanitation systems and as an indicator of the potential role of water in disease outbreaks. Moreover, since the natural host for all human enteroviruses is humans, the detection and quantification of amplifiable enterovirus genetic material in environmental waters has been proposed and successfully used as a water quality assessment tool for tracking sources of human fecal pollution.