Genetic diversity of norovirus in hospitalised diarrhoeic children and asymptomatic controls in Dar es Salaam, Tanzania

Stool specimens and demographic/clinical information, were prospectively collected from 705 hospitalised children with diarrhoea (cases) and 561 children without diarrhoea (controls) between 2010 and 2011. Norovirus detection was done by real-time RT-PCR. Genotype was determined using Gel-based and real time RT-PCR methods and sequencing targeting the polymerase and the capsid region respectively. Norovirus was detected in 14.3%, 181/1266 children. The prevalence of norovirus was significantly higher in cases (18.3%, 129/705) than in controls, (9.2%, 52/561), P < 0.05. Except for one child who had double infection with GI and GII all 129 cases had GII. Among controls, 23.1% had GI and 76.9% had GII. Norovirus GII.4 was significantly more prevalent in cases 87.9% than in controls 56.5%. Other genotypes detected in both cases and controls were GII.21, GII.16 and GII.g. The highest numbers of norovirus were detected in April 2011. The number of norovirus detected was significantly higher during the first than second year of life (109/540, 20.2% vs. 20/165, 12.1%). The prevalence of norovirus in HIV-positive and negative children was (21.2%, 7/33) and (10.3%, 40/390, P = 0.05) respectively, regardless of diarrhoea symptoms. No significant difference in gender, parent's level of education or nutritional status with norovirus infection was observed within cases or controls. This study confirms the significant role of norovirus infection, especially GII.4 in diarrhoeic children who need hospitalisation and adds knowledge on norovirus epidemiology in the African region.