Volume 14, Number 10—October 2008 Norwalk Virus Shedding after
Experimental Human Infection Noroviruses are the most common
cause of viral gastroenteritis in the United States. To
determine the magnitude and duration of virus shedding in feces,
we evaluated persons who had been experimentally infected with
Norwalk virus. Of 16 persons, clinical gastroenteritis (watery
diarrhea and/or vomiting) developed in 11; symptomatic illness
lasted 1–2 days. Virus shedding was first detected by reverse
transcription–PCR (RT-PCR) 18 hours after participant
inoculation and lasted a median of 28 days after inoculation
(range 13–56 days). The median peak amount of virus shedding was
95 × 109 (range 0.5–1,640 ×109) genomic copies/g feces as
measured by quantitative RT-PCR. Virus shedding was first
detected by antigen ELISA ≈33 hours (median 42 hours) after
inoculation and lasted 10 days (median 7 days) after
inoculation. Understanding of the relevance of prolonged fecal
norovirus excretion must await the development of sensit