Figure 1. Shedding of Norwalk virus in feces. The quantity of viral RNA measured by quantitative reverse transcription–PCR (qRT-PCR; black line) and of virus antigen measured by ELISA (optical density; blue line) is shown for 2 participants: no. 703, who did not have clinical gastroenteritis (panel A), and no. 721, who had clinical gastroenteritis (panel B). Vertical lines represent the period of clinical symptoms; N, nausea; V, vomiting. Panels C, D, and E show the virus titers as measured by qRT-PCR in fecal samples collected from participants who had no clinical gastroenteritis, had gastroenteritis with vomiting only, and had gastroenteritis with vomiting and diarrhea, respectively.