The RNA extracts were then subjected to the testing process for NoV detection with real-time PCR using a Corbet Research Rotor Gene 6000 platform [29]. with RT-PCR and Sanger sequencing. ELISA using NoV VLP (virus-like particles) GII.4 as antigens was performed around the saliva specimens. Dehydrated children were predominantly those with NoV infections (65/74, 88%; < 0.0001). NoV-positive infections were significantly associated with the severe diarrhea cases having a high vesikari score (55%, 33/60) when compared to DIAPH2 the non-severe diarrheal score (29.3%, 41/140; < 0.0308). NoV of the GII genogroup was mainly detected in severe diarrhea cases (50.9%, 30/59; = 0.0036). The geometric means of the NoV-specific IgA level were higher in the asymptomatic NoV-infected group (0.286) as compared to the symptomatic group (0.174). This obtaining suggests that mucosal immunity may not protect the children from the NoV contamination. However, the findings indicated the contribution of the pre-existing NoV-specific IgA immune response in reducing the severity of diarrheal disease. A high vesikari score of AGE associated with the NoV GII genogroup circulating in the study area underscores the need for an appropriate treatment of AGE based on the severity level of NoV-associated clinical symptoms in young children. Keywords: vesikari score, specific IgA, diarrhea, NoV infections, symptomatic, asymptomatic, young children 1. Introduction Diarrheal disease in children under 5 years of age is a public health concern in low-resource settings [1,2]. With the substantial decrease in rotavirus-associated diarrhea in the countries that have implemented routine rotavirus vaccination, NoV has emerged as the leading cause of AGE [3,4,5]. In South Africa, the rotavirus vaccination was introduced in 2009 2009. NoV infections are responsible Glycopyrrolate for approximately 700 million episodes of diarrhea annually worldwide with considerable morbidity and mortality. There is no specific treatment against NoV infections, and no vaccines are available [6,7]. Appropriate treatment of AGE based on the level of clinical symptoms associated with detected NoV infections [8] can help to avoid the complications of AGE and hospitalizations. Usually, in clinical practice, there is no confirmation of a viral AGE-causing agent in real-time, particularly in rural areas with limited laboratory facilities. The vesikari clinical severity system has been considered as the best predictor tool to categorize the severity of AGE and help to determine the treatment level of diarrheal disease [9,10,11]. However, data that include the severity scores for NoV-associated AGE in South Africa are scarce [12]. There are no licensed vaccines Glycopyrrolate against NoV. Previous reports have exhibited the evidence of vaccine-induced protective immunity against NoV in young children [13,14]. As NoV is an enteric computer virus that infects the mucosal surfaces of the gastrointestinal tract, it is evident that mucosal immunity will play a critical role in protection against NoV contamination [15]. An effective enteric viral vaccine should induce a sufficient level of intestinal IgA antibodies to protect against viral contamination Glycopyrrolate in the gastrointestinal tract [16,17,18,19]. Previous NoV studies have demonstrated that the level of pre-existing salivary IgA antibodies correlated with minor risk of contamination and restricted severity of gastroenteritis [18,20,21,22,23]. NoV investigations that evaluate the impact of pre-existing mucosal immunity in NoV infections are needed to contribute to the development of an effective NoV vaccine [15,22,23]. Virus-like particle (VLP)-derived vaccines are currently under development [21,22,23]. In South Africa, no data have been reported around the role of mucosal immunity, specifically IgA Glycopyrrolate antibodies, in NoV infections among young children. Previous studies from rural communities in South Africa reported a high prevalence rate and diversity of Norovirus circulating associated with AGE [24,25]. In the present study, an Elisa-based method to detect NoV-specific IgA in the saliva samples was performed. The main obtaining was that NoV-specific mucosal levels correlated with limited severity of Glycopyrrolate AGE. This study aimed to determine the presence of pre-existing.