Pediatric norovirus GII.4 infections in Nicaragua, 1999–2015

Abstract

Objectives Investigate clinical and epidemiological factors of pediatric GII.4 norovirus infections in children with acute gastroenteritis (AGE) in Nicaragua between 1999 and 2015. Methods We retrospectively analyzed laboratory and epidemiologic data from 1,790 children ≤ 7 years with AGE from 6 hospitals in Nicaragua (n = 538), and 3 community clinics (n = 919) and households (n = 333) in León, between 1999 and 2015. Moreover, asymptomatic children from community clinics (n = 162) and households (n = 105) were enrolled. Norovirus was detected by real-time PCR and genotyped by sequencing the N-terminal and shell region of the capsid gene. Results Norovirus was found in 19% (n = 338) and 12% (n = 32) of children with and without AGE, respectively. In total, 20 genotypes including a tentatively new genotype were detected. Among children with AGE, the most common genotypes were GII.4 (53%), GII.14 (7%), GII.3 (6%) and GI.3 (6%). In contrast, only one (1.4%) GII.4 was found in asymptomatic children. The prevalence of GII.4 infections was significantly higher in children between 7 and 12 months of age. The prevalence of GII.4 was lowest in households (38%), followed by community clinics (50%) and hospitals (75%). Several different GII.4 variants were detected and their emergence followed the global temporal trend. Conclusions Overall our study found the predominance of pediatric GII.4 norovirus infections in Nicaragua mostly occurring in children between 7 and 12 months of age, implicating GII.4 as the main norovirus vaccine target.

Norovirus transmission mediated by asymptomatic family members in households

“…A community-based epidemiological study showed that asymptomatic infections peak during the winter season in England [14], where seasonal symptomatic infections occur in the winter season [63]. Similar seasonal asymptomatic NV infections have been observed in Korea [64,65] and Nicaragua [21]. As described above, symptomatic and asymptomatic infections also have similarities to the prevalent genotypes.…”

“…It has been reported that the distribution of genotypes detected from symptomatic children is quite different from that of asymptomatic children [21]. Simultaneous analyses of symptomatic and asymptomatic individuals of all age groups in the same settings may clarify the relationship between symptomatic and asymptomatic individuals regarding the prevalence of genotypes and their seasonal synchronicity.…”

“…The ratio of asymptomatic NV infections ranges from <1% to >30%, depending on the setting [5,12]. Asymptomatic NV infection occurs in all age groups, including children and infants [13][14][15][16][17][18][19][20][21]. A comprehensive analysis of the attack rates of NV during outbreaks suggested that asymptomatic infections occur in a proportion of the population [22].…”

Genetic Susceptibility to Human Norovirus Infection: An Update

“…Moreover, secretors would be susceptible to both secretor and secretor-independent genotypes (Figure 2). These factors suggest that populations with a higher prevalence of secretors would have more infections, and perhaps a higher disease burden, especially since some studies have suggested that GII.4 cause more clinically severe disease [59,60,61].…”

“…Norovirus is commonly found in asymptomatic healthy individuals, with a prevalence ranging from 5–15% [66,67]. The clinical outcome of norovirus infection is partly genotype-dependent, with studies demonstrating that the predominant GII.4 genotype causes more severe symptoms and is relatively less prevalent in asymptomatic controls compared to other genotypes [53,60,61,66]. The GII.4 genotype has also been reported to be shed in higher titers compared to other genotypes [59,68].…”