Prolonged Shedding of Norwalk Virus in Feces

Noroviruses, the most common cause of viral gastroenteritis in the U.S., are responsible for an estimated 23 million cases per year. To better understand fecal excretion of Norwalk virus, researchers in Texas challenged healthy adults aged 18 to 50 with oral doses of Norwalk virus ranging from 4.8 to 4800 reverse-transcriptase (RT)-PCR units. After challenge, participants were observed for ≥96 hours in a research center. Thereafter, fecal samples were collected daily for 21 days and then weekly for ≤5 additional weeks.

Eleven of 16 participants who met the criteria for Norwalk virus infection had gastroenteritis, as defined by the research protocol. Median duration of symptoms and signs was 23 hours (range, 10–61 hours). Viral shedding as me…