Abstract:An investigation was undertaken to determine the effect of chlorine on a small DNA-containing enteric virus. Parvovirus H-1 was exposed to sodium hypochlorite in a phosphate-buffered saline solution at pH 7. Then, the whole virion, the protein capsid, or the nucleic acid was subjected to analysis. The sedimentation rate of the chlorine-treated whole virus decreased from 110S to 43S. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the virus demonstrated the formation of higher-molecular-weight aggr… Show more
“…In fact, very little is known about viral genome degradation in the environment or during water treatment. Data specifically concerning the degradation of the capsid or the genome by oxidants are sparse and sometimes contradictory (O'Brien and Newman 1979;Kim et al 1980;Roy et al 1981;O'Brien 1982a, 1982b;Churn et al 1983;Hauchman et al 1986;Noss et al 1986). In particular, no quantitative approach for viral genome degradation has been investigated in terms of the impact of oxidants on viral particles in water.…”
Aims: This study was undertaken to gain an understanding of the factors that influence viral RNA degradation in the presence of chlorine dioxide (ClO2), which will be very useful in helping to define the significance of the presence of the viral genome in disinfected water.
Methods and Results: We focused our investigation on the influence of ClO2 on extracted RNA on the one hand, and on the infectious virus on the other. Our first results show that RNA degradation, like viral inactivation, is dose dependent. The influence of the spatial organization of the targeted genomic sequence, as well as that of its size and location (and/or sequence) on degradation of the Poliovirus 1 genome by ClO2, was studied using real‐time reverse transcriptase‐polymerase chain reaction (RT‐PCR). The results show that the preferential sites of action of ClO2 appear to be located in the untranslated regions, 5′‐ and 3′‐UTR, a phenomenon influenced by both the presence of secondary structures and the genomic sequence in these regions. Our results also reveal a rapid decrease of infectious particles quantified by the cell culture for the applied dose. Comparison between cell culture and real‐time PCR for viral detection reveals disagreement following disinfection treatment, even for the largest targeted fragment (a 6989‐base fragment representing the quasi‐whole viral genome).
Conclusions: The detection of genome fragments is insufficient to confirm the presence of the infectious virus, as each targeted fragment shows a different sensitivity. Hence, the smallest targeted fragment (76 bp) persisted throughout the analysis period, while the longest targeted fragment (6989 bp) disappeared very rapidly. Highly sensitive regions (i.e. 5′‐ and 3′‐UTR) should be targeted to avoid an overestimation of the risk of viral infection using molecular biology methods in water following disinfection. Further studies in this area are needed.
Significance and Impact of the Study: To date, it has not been possible to routinely apply virological controls to drinking water because of the time‐consuming nature of the gold standard technique (cell culture) and its inability to detect all serotypes (e.g. Norovirus). Molecular techniques (e.g. real‐time RT‐PCR) constitute a solution to the rapid and specific detection of all the serotypes. However, ignorance of the mechanisms of viral degradation prevents the validation of PCR for the measurement of the risk of infection to humans following disinfection treatment.
“…In fact, very little is known about viral genome degradation in the environment or during water treatment. Data specifically concerning the degradation of the capsid or the genome by oxidants are sparse and sometimes contradictory (O'Brien and Newman 1979;Kim et al 1980;Roy et al 1981;O'Brien 1982a, 1982b;Churn et al 1983;Hauchman et al 1986;Noss et al 1986). In particular, no quantitative approach for viral genome degradation has been investigated in terms of the impact of oxidants on viral particles in water.…”
Aims: This study was undertaken to gain an understanding of the factors that influence viral RNA degradation in the presence of chlorine dioxide (ClO2), which will be very useful in helping to define the significance of the presence of the viral genome in disinfected water.
Methods and Results: We focused our investigation on the influence of ClO2 on extracted RNA on the one hand, and on the infectious virus on the other. Our first results show that RNA degradation, like viral inactivation, is dose dependent. The influence of the spatial organization of the targeted genomic sequence, as well as that of its size and location (and/or sequence) on degradation of the Poliovirus 1 genome by ClO2, was studied using real‐time reverse transcriptase‐polymerase chain reaction (RT‐PCR). The results show that the preferential sites of action of ClO2 appear to be located in the untranslated regions, 5′‐ and 3′‐UTR, a phenomenon influenced by both the presence of secondary structures and the genomic sequence in these regions. Our results also reveal a rapid decrease of infectious particles quantified by the cell culture for the applied dose. Comparison between cell culture and real‐time PCR for viral detection reveals disagreement following disinfection treatment, even for the largest targeted fragment (a 6989‐base fragment representing the quasi‐whole viral genome).
Conclusions: The detection of genome fragments is insufficient to confirm the presence of the infectious virus, as each targeted fragment shows a different sensitivity. Hence, the smallest targeted fragment (76 bp) persisted throughout the analysis period, while the longest targeted fragment (6989 bp) disappeared very rapidly. Highly sensitive regions (i.e. 5′‐ and 3′‐UTR) should be targeted to avoid an overestimation of the risk of viral infection using molecular biology methods in water following disinfection. Further studies in this area are needed.
Significance and Impact of the Study: To date, it has not been possible to routinely apply virological controls to drinking water because of the time‐consuming nature of the gold standard technique (cell culture) and its inability to detect all serotypes (e.g. Norovirus). Molecular techniques (e.g. real‐time RT‐PCR) constitute a solution to the rapid and specific detection of all the serotypes. However, ignorance of the mechanisms of viral degradation prevents the validation of PCR for the measurement of the risk of infection to humans following disinfection treatment.
“…After chlorination, chlorine reacts more with intracellular components, meaning that the cells show better structural integrity and less plasma leakage because the diffusion of chlorine into cells is less constrained by reactions with cell walls. Chlorination is influenced by factors similar to ozone disinfection ( Churn et al 1983 , Cho et al 2010 ). Schema 7 Inactivation of some microorganisms when using chlorination in water.…”
Section: Effect Of Chlorination On Sars-cov-2mentioning
“…Chlorine inactivates viruses by damaging the viral capsids and destroying the exposed nucleic acids [ 55 , 56 ]. Specific sites of viral capsids are highly reactive [ 56 ], which may be explained by the different reactivity of chlorine with amino acids [ 57 ]. There is also a sensitive sequence to chlorination in viral genome.…”
Section: The Removal Of Viruses By Chlorinationmentioning
The COVID-19 pandemic draws much attention to virus inactivation since the SARS-CoV-2 was detected in miscellaneous environments and the wastewater can be a potential transmitting pathway. UV irradiation, ozonation and chlorination are widely used disinfection processes in water treatment. In this review, the mechanisms and applications of three disinfection processes are introduced, and their inactivation effects on virus as well as other microorganisms are compared and discussed. The resistance of viruses to UV irradiation is generally stronger than that of bacteria. 4-log inactivation of bacteria can be easily obtained within a UV dose of 10 mJ/cm
2
. However, the doses to reach the same virus removal rate vary greatly from 10 to 140 mJ/cm
2
. The coronaviruses have even stronger UV resistance. Comparatively, ozonation and chlorination are effective methods to inactivate viruses, and the CT values of 4-log removal for most viruses concerned are lower than 1 mg·min/L and 10 mg·min/L, respectively. Protozoa, fungal spores and bacterial spores are more resistant to disinfection. Temperature, pH, organic matters, turbidity and other parameters all have influences on the disinfection. With a 10 °C decrease in temperature, the CT value required for certain removal rates doubles. Generally low pH promotes disinfection and high pH is against it. In drinking water and wastewater treatment process, the resistance properties of microorganisms and other influence parameters should be taken into consideration when choosing disinfection technologies.
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