Detectie van Norwalk-like calicivirussen en rotavirussen in rioolwater in relatie tot explosies van gastro-enteritis

In this study we describe a molecular method for the detection of a Norwalk-like virus (NLV) and a rotavirus (RNA) in sewage water concentrates. This includes its application in the monitoring of raw sewage in conjunction with confirmed outbreaks of viral gastro-enteritis. The virus was concentrated from the raw sewage by (conventional) filter adsorption-elution, followed by a two-phase separation. RNA was extracted from the final concentrate through binding to glassbeads. NLV was detected by reverse-transcriptase chain reaction amplification (RT-PCR) in all initial sewage samples collected at locations where an outbreak of gastro-enteritis had been reported. Nucleotide sequence analysis of the PCR products revealed the patient strains and the strains found in the initial sewage samples to be identical. At two of these locations rotavirus was also found in the sewage samples. In addition, NLV was detected by RT-PCR in 10 of the 11 follow-up samples, and rotavirus in 7 of these. After cloning 10 of the NLV-RT-PCR products and nucleotide sequence analysis of 5 clones per sample, 6 out of 10 specimens were found to contain multiple NLV genotypes, indicating co-circulation of several types. The remaining four sewage extracts contained only one genetic type of NLV. The amount of virus in the samples was estimated by testing 10-fold serial dilutions using RT-PCR; this amount was found to be quite variable, with maximum levels as high as 10-7RNA-containing particles per litre. Our findings imply a potential risk in waterborne transmission of NLV and rotavirus. The burden of illness due to NLV or rotavirus is also suggested to be with associated gastro-enteritis in the general population, where it is higher than has been estimated from investigations of outbreaks