Abstract
BackgroundHuman caliciviruses (HuCV) are emerging enteric pathogens that are a common cause of diarrhea in humans worldwide. Due to the paucity of information on the molecular characterization of HuCV circulating in Mexico, the aim of this work was to investigate the diversity and molecular epidemiology of the HuCV infection associated with acute diarrheal disease in Mexican children aged up to 5 years.ResultsOf the 131/414 (32%) HuCV positive-specimens analyzed, 128 were identified as Norovirus (NoV) and three as Sapovirus (SaV). Of the NoV positive specimens, 118/128 (92%) were NoV GII and 10/128(8%) were untypeable by RT-PCR in both polymerase and capsid genes, whereas one SaV isolate was further confirmed by sequencing as GI.2. Phylogenetic analysis based on polymerase partial gene sequences from 89/131 (68%) HuCV isolates showed that 86/89 (97%) belong to NoV GII.4 with three main variant clusters of this genotype, 2/89 (2%) to NoV GII.2, and 1/89 (1%) to SaV GI.2. Furthermore, partial sequencing of the capsid gene VP1 of 63/131 (48%) strains indicated that 61/63 (97%) correlated with NoV GII.4, whereas only 2/63 (3%) clustered to NoV GII.2. HuCV infections were detected throughout the year, and the highest number of cases positive for NoV was found in children between 7 and 18 months of age (60%).ConclusionsThis study highlights the usefulness of analyzing both polymerase and capsid genes for molecular characterization of HuCV and demonstrates the relatedness and predominance of NoV GII.4 with acute diarrheal disease in young Mexican children, thus contributing to better understanding of the molecular epidemiology of this disease.
Highlights
Human caliciviruses (HuCV) are emerging enteric pathogens that are a common cause of diarrhea in humans worldwide
The Reverse transcription-polymerase chain reaction (RT-PCR) reaction performed to genotype the 128 NoV-positive samples employing primers targeted toward the Polymerase gene (RdRp) gene indicated that 72/128 (56%) viral strains belong to NoV Genogroup II of norovirus (GII), whereas no sample was amplified for NoV GI or for a combination of GI and GII
Of 56 NoV positive samples that were negative for the RdRp genotyping reaction, it was possible to identify 46/56 samples for a total of 118/128 for NoV GII, with primers targeted toward the capsid gene (Table 1) (Figure 1)
Summary
Human caliciviruses (HuCV) are emerging enteric pathogens that are a common cause of diarrhea in humans worldwide. Due to the paucity of information on the molecular characterization of HuCV circulating in Mexico, the aim of this work was to investigate the diversity and molecular epidemiology of the HuCV infection associated with acute diarrheal disease in Mexican children aged up to 5 years. Mortality due to diarrheal disease has been reported in > 1 million human deaths annually, with young children comprising the most important age group affected [1]. Human caliciviruses (HuCV) include the genera Norovirus (NoV) and Sapovirus (SaV); in particular, NoV has been recognized as the most important cause of nonbacterial, acute gastroenteritis in humans of all age groups. SaV strains that belong to genogroup I have been detected predominantly over the last decade in Japan, whereas NoV GII. is the major cause of acute, nonbacterial gastroenteritis and food-related outbreaks circulating worldwide [5,6]
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