A 9-month-old child is brought to the Health Depament to receive the second dose of oral polio vaccine, 2 weeks after the first vaccination. The child has mild diarrhea, so the decision is made to defer fuher immunizations. Bacteriologic examination of a stool culture is unremarkable; however, a small, single-stranded, positive RNA virus is isolated from the specimen. The viral isolate was not inactivated by ether. Which of the following viruses was most likely isolated?

Poliovirus, which is a single-stranded +RNA virus, is naked (i.e., non-enveloped) and hence will not be inactivated by lipid solvents such as ether. The live virus vaccine had colonized the intestinal tract of the infant and was still being shed 2 weeks after the earlier oral dose. This same virus, the vaccine strain, is likely to be found in sewage, as all vaccinated infants will shed virus for a period of time after immunization with OPV. Adenoviruses and parvovirus B19 also may cause diarrheal disease and both are non-enveloped; however, they both have a DNA genome. Hepatitis C is an enveloped, single-stranded +RNA virus; its major target organ is the liver, not the intestinal tract. It is a fragile agent that does not survive well outside the body and would not be isolated from raw sewage effluent.