Recovering viruses from sewage, effluents, and water

Waterborne outbreaks of disease produced by hepatitis A virus (enterovirus 72), rotaviruses, Norwalk and Norwalk-like agents, and other enteric viruses are now well documented. ¹ - ⁵ It is now clear that the Norwalk agent is a major cause of waterborne nonbacterial gastroenteritis in the U.S. ⁵ While difficult to prove because of limitations of epidemiology and a lack of methods for detection, other groups of enteric viruses, such as the enteroviruses, most surely are responsible for undocumented waterborne disease. Recent studies with human volunteers have clearly shown that small numbers of enteric viruses delivered by the water route can cause disease. ⁶ The presence of even one virus, detectable in tissue culture, in a water supply poses a potential disease hazard. It has been calculated that if a water supply contains as little as one plaque-forming unit of virus per 50 gal of drinking water in a community utilizing 50 mgd (0.2% of which is ingested as drinking water), at a 30% infection rate, 600 individuals would daily contract a variety of clinical and subclinical infections. ⁷ Thus, most current and proposed standards for viruses in water (Table 1) suggest methods capable of detecting viruses in 10 to 1000 ℓ of water.