shed in feces in high quantity (up to 10
11 particles per gram of stool) for a few days
up to several weeks [55]. Consequently, domestic wastewaters are often highly
contaminated with human enteric viruses [56, 57]. These viruses are relatively
resistant to various water treatments and environmental conditions and persist in
the environmental waters for long periods of time. Moreover, the viruses can infect a
host at a low infectious dose, from 10 to 1,000 viral particles, independently of
individual immunity and genetic susceptibility to infection [58].
Estimating the risk associated with the presence of enteric viruses in the water is
not a simple task. While the microbiological quality of drinking water and recreational waters is mainly based on the presence of FIBs, as described in Sect. 3, these
bacteria are generally less able to persist in water and resist water treatments at a
lower level than human enteric viruses. Consequently, these bacterial indicators
could not be directly used to assess the viral risk [59, 60].
The estimation of risk for human health, linked to viruses in the environment, is
based on the detection of infectious viruses that infect permissive cells. However,
most viruses are not easily cultivable. The detection based on virus genome amplification bypasses the cultivation limitation, but genome detection does not systematically imply health risk since partially intact genomes from noninfectious particles
could be amplified. The evaluation of virus capsid integrity offers complementary
information. A study conducted with samples from the Seine River in the Paris area
showed that few differences were observed between the detection of total genomes
and encapsidated genomes [61]. These results suggest that most viruses detected in
natural waters in the Paris agglomeration have intact capsids and are therefore
potentially infectious. This study also suggests that virus detection by molecular
methods such as real-time PCR provides a true image of the viral danger present in
surface waters.
Human enteric viruses were extensively monitored using an integrity assay in the
Seine River (Paris area) for several years. The results presented in Fig. 11 showed
significant contamination with the viruses the most frequently implicated in gastroenteritis in humans. In the Seine River, the median value was 10,470 genome units
(GU)/L for total adenovirus and 1,026 GU/L for type F adenovirus. The type F
adenovirus (serotypes 40 and 41) accounted for about 10% of total adenoviruses.
The main virus responsible for gastroenteritis in humans (norovirus) is titrated at
216 GU/L and 146 UG/L for human norovirus GI and GII, respectively. The median
concentration for type A rotavirus was 4,082 GU/L. Somatic coliphages were
detected by culture with a median value of 1,350 PFU/L and F-specific RNA
coliphages titrated at 460 GU/L.
Similar results were obtained for the Marne River (data not shown). The median
values were 39,800 GU/L and 2,200 GU/L for total and type F adenoviruses,
respectively; 1,550 UG/L and 976 GU/L for human noroviruses GI and GII,
respectively; and 7,026 GU/L for type A rotavirus. Viral indicators were titrated at
1700 GU/L and 15,262 GU/L for somatic and F-specific RNA coliphages, respectively. In both rivers, human enteroviruses (including poliovirus) were infrequently
detected.
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J.-M. Mouchel et al.
11 particles per gram of stool) for a few days
up to several weeks [55]. Consequently, domestic wastewaters are often highly
contaminated with human enteric viruses [56, 57]. These viruses are relatively
resistant to various water treatments and environmental conditions and persist in
the environmental waters for long periods of time. Moreover, the viruses can infect a
host at a low infectious dose, from 10 to 1,000 viral particles, independently of
individual immunity and genetic susceptibility to infection [58].
Estimating the risk associated with the presence of enteric viruses in the water is
not a simple task. While the microbiological quality of drinking water and recreational waters is mainly based on the presence of FIBs, as described in Sect. 3, these
bacteria are generally less able to persist in water and resist water treatments at a
lower level than human enteric viruses. Consequently, these bacterial indicators
could not be directly used to assess the viral risk [59, 60].
The estimation of risk for human health, linked to viruses in the environment, is
based on the detection of infectious viruses that infect permissive cells. However,
most viruses are not easily cultivable. The detection based on virus genome amplification bypasses the cultivation limitation, but genome detection does not systematically imply health risk since partially intact genomes from noninfectious particles
could be amplified. The evaluation of virus capsid integrity offers complementary
information. A study conducted with samples from the Seine River in the Paris area
showed that few differences were observed between the detection of total genomes
and encapsidated genomes [61]. These results suggest that most viruses detected in
natural waters in the Paris agglomeration have intact capsids and are therefore
potentially infectious. This study also suggests that virus detection by molecular
methods such as real-time PCR provides a true image of the viral danger present in
surface waters.
Human enteric viruses were extensively monitored using an integrity assay in the
Seine River (Paris area) for several years. The results presented in Fig. 11 showed
significant contamination with the viruses the most frequently implicated in gastroenteritis in humans. In the Seine River, the median value was 10,470 genome units
(GU)/L for total adenovirus and 1,026 GU/L for type F adenovirus. The type F
adenovirus (serotypes 40 and 41) accounted for about 10% of total adenoviruses.
The main virus responsible for gastroenteritis in humans (norovirus) is titrated at
216 GU/L and 146 UG/L for human norovirus GI and GII, respectively. The median
concentration for type A rotavirus was 4,082 GU/L. Somatic coliphages were
detected by culture with a median value of 1,350 PFU/L and F-specific RNA
coliphages titrated at 460 GU/L.
Similar results were obtained for the Marne River (data not shown). The median
values were 39,800 GU/L and 2,200 GU/L for total and type F adenoviruses,
respectively; 1,550 UG/L and 976 GU/L for human noroviruses GI and GII,
respectively; and 7,026 GU/L for type A rotavirus. Viral indicators were titrated at
1700 GU/L and 15,262 GU/L for somatic and F-specific RNA coliphages, respectively. In both rivers, human enteroviruses (including poliovirus) were infrequently
detected.
344
J.-M. Mouchel et al.