Norovirus Loads in Stool Specimens of Cancer Patients with Norovirus Gastroenteritis

In immunocompromised patients with norovirus (NoV) gastroenteritis, the relationship between fecal NoV load and clinical complications has not been examined. In this study, a validated real-time quantitative PCR assay was used to determine viral loads for NoV genogroup I and II (GI and GII) in NoV-positive stool specimens of cancer patients. A total of 234 specimens from 152 patients were positive for NoV, including 201 of GII and 33 of GI. Geometric mean of logarithmic copies per gram of stool (w/w) of NoV-GII were 9.03 ± 1.71 (means ± SD), which was significantly higher than that of NoV-GI [7.87 ± 1.49; odd ratio (OR), 3.22; 95% CI, 1.33-7.76; P = 0.009]. Among 152 patients with gastroenteritis, the fecal NoV geometric mean of logarithmic copy was correlated with mild (n = 85; 7.97 ± 1.55), moderate (n = 23; 9.09 ± 1.38), and severe (n = 44; 10.39 ± 0.91) episodes of severity by modified Vesikari scoring system, respectively. Multivariate analysis revealed that high level of NoV load was correlated with GII infections (OR, 4.13; 95% CI, 1.62-10.55; P = 0.003) and associated with development of severe clinical symptom (OR, 5.53; 95% CI, 2.00-7.24; P = 0.001) at the time of diagnosis. Infection with GII strains was more common than GI infection in cancer patients with viral gastroenteritis.