Detection of Norovirus in Saliva Samples from Acute Gastroenteritis Cases and Asymptomatic Subjects: Association with Age and Higher Shedding in Stool

Abstract

Norovirus infections are a leading cause of acute gastroenteritis outbreaks worldwide and across all age groups, with two main genogroups (GI and GII) infecting humans. The aim of our study was to investigate the occurrence of norovirus in saliva samples from individuals involved in outbreaks of acute gastroenteritis in closed and semiclosed institutions, and its relationship with the virus strain, virus shedding in stool, the occurrence of symptoms, age, and the secretor status of the individual. Epidemiological and clinical information was gathered from norovirus outbreaks occurring in Catalonia, Spain during 2017–2018, and stool and saliva samples were collected from affected and exposed resident individuals and workers. A total of 347 saliva specimens from 25 outbreaks were analyzed. Further, 84% of individuals also provided a paired stool sample. For GII infections, norovirus was detected in 17.9% of saliva samples from symptomatic cases and 5.2% of asymptomatic individuals. Positivity in saliva occurred in both secretors and nonsecretors. None of the individuals infected by norovirus GI was positive for the virus in saliva. Saliva positivity did not correlate with any of the studied symptoms but did correlate with age ≥ 65 years old. Individuals who were positive in saliva showed higher levels of virus shedding in stool. Mean viral load in positive saliva was 3.16 ± 1.08 log10 genome copies/mL, and the predominance of encapsidated genomes was confirmed by propidium monoazide (PMA)xx-viability RTqPCR assay. The detection of norovirus in saliva raises the possibility of oral-to-oral norovirus transmission during the symptomatic phase and, although to a lesser extent, even in cases of asymptomatic infections.

Enteric viruses replicate in salivary glands and infect through saliva

“…2 , 3 , 9 – 11 ). Norovirus, rotavirus and astrovirus genomic RNA have been frequently detected in saliva in symptomatic and asymptomatic individuals 12 – 14 . These observations were interpreted as gut contaminants because these viruses are thought to mainly transmit through the fecal–oral route by ingestion of contaminated food and water and productively replicate in the intestines 1 , 15 – 18 .…”

Household Surveillance for Norovirus Gastroenteritis in a Nicaraguan Birth Cohort: A Nested Case—Control Analysis of Norovirus Risk Factors

“…This finding supports a recent report that, in a mouse model, norovirus can replicate in salivary glands and infect through saliva [ 22 ]. In humans, PCR detection of norovirus in the saliva of infected individuals has been associated with recent vomiting [ 23 ] and higher viral load in feces [ 24 ]. This finding of potential oral–oral transmission is important when considering measures to prevent norovirus spread.…”

Infectious Etiology of Vomiting in Children With Presumed Acute Gastroenteritis in the Absence of Diarrhea: Protocol for a Cohort Study

“…infectious etiologies vomiting in the absence of diarrhea (11)(12)(13)(14)(15). A recent study by Freedman et al (16) suggests that, in children presenting to emergency departments with presumed AGE with isolated vomiting, an enteropathogen can be identified using rectal swabs and molecular diagnostic tests.…”