Monitoring of seasonality of norovirus and other enteric viruses in Cameroon by real-time PCR: an exploratory study

Abstract

We studied the seasonal fluctuation of norovirus and other enteric viruses in Cameroon. Two hundred participants aged between 1 and 69 years were prospectively followed up. Each participant provided monthly faecal samples over a 12-month period. A total of 2484 samples were tested using multiplex real-time PCR assay for the detection of norovirus, rotavirus and enterovirus. The effect of weather variables and risk factors were analysed by Pearson correlation and bivariate analysis. Overall, enterovirus was the most commonly detected virus (21·6% of specimens), followed by norovirus (3·9%) and rotavirus (0·4%). Norovirus and enterovirus were detected throughout the year with a peak of norovirus detection at the beginning of the rainy season and a significant alternation of circulation of norovirus genogroups from one month to the next. Age <5 years and consumption of tap water were risk factors for norovirus infection. Better understanding of factors influencing transmission and seasonality may provide insights into the relationship between physical environment and risk of infection for these viruses.

Pattern of Circulation of Norovirus GII Strains during Natural Infection

“…NoV RNA was detected by real-time PCR as described previously (3). Briefly, the assay was performed in 25-l reaction volumes containing 5 l nucleic acid, 13.5 l 2ϫ reaction mix with ROX (Invitrogen Ltd., Paisley, United Kingdom), 0.5 l Superscript III platinum onestep quantitative reverse transcription-PCR (RT-PCR) mix, 20 U RNase-OUT, and 0.5 M primers and probes published elsewhere (21).…”

“…Reverse transcription (cDNA synthesis) was carried out as described previously (3). Briefly, 5 l of nucleic acid was added to 45 l of a reaction mix consisting of 100 M each deoxynucleoside triphosphate (dNTP; Amersham Biosciences, Piscataway, NJ), 2 l 5ϫ reaction buffer (Invitrogen, Carlsbad, CA), 0.01 M dithiothreitol, 20 U RNasin (Promega Corp., Madison, WI), 100 U SuperScript II reverse transcriptase (Invitrogen), and random hexamer primers (Promega, United Kingdom).…”

“…In tropical regions, infections are relatively common in the rainy season (3). The virus is a small nonenveloped, singlestranded, positive-sense RNA virus with a genome of about 7.5 kb in size classified in the Caliciviridae family (4).…”

Role of noroviruses as aetiological agents of diarrhoea in developing countries

“…We and other investigators have detected noroviruses in persons without gastroenteritis in prospective longitudinal studies, suggesting that asymptomatic infection may be relatively common (Ayukekbong et al, 2013;Bucardo et al, 2010;Zhang et al, 2011). The length of observation in these studies suggests that asymptomatic infection is not necessarily occurring as pre-or post-symptomatic shedding of the virus.…”

“…Noroviruses of an extensive genomic and antigenic diversity co-circulate in the human population (Bruggink et al, 2015). In Africa, there is evidence of a rainy season peak of norovirus infection and water is increasingly recognized to play a role in the transmission (Ayukekbong et al, 2013), although documentation of water-borne outbreaks of gastroenteritis is scarce in that continent. This review seeks to extend knowledge on the epidemiology and the burden of norovirus infection in developing countries as compared with industrialized countries.…”