Perspectives in medical virology最新文献

Viruses in water are usually present in concentrations too low for detection by direct analysis. Virological investigation of water samples is always a multi-stage process involving concentration of viruses present followed by an appropriate detection procedure. There are several approaches to detection of viruses. Part or all of the concentrate may be inoculated into cell cultures to detect infectious cytopathogenic virus, and if this is done in a quantitative fashion the virus can be enumerated, the count being reported as plaque-forming units, the tissue culture infectious dose, or most probable number units. The virus may be isolated and identified from the cell cultures. Viruses that multiply without producing an identifiable cytopathic effect in culture may sometimes be detected by immunoperoxidase or immunofluorescence staining. The concentrate may also be analyzed by molecular biological procedures (usually polymerase chain reaction (PCR) or real-time-PCR). The problem then is that such techniques do not usually detect the infectious virus, and novel approaches have been made recently to meet this challenge.

This chapter illustrates the recommendations and guidelines of the World Health Organization (WHO) concerning water, sanitation, and health. The recommendations and guidelines are evaluated in the light of disease caused by human pathogenic viruses. The guidelines outline a preventive management framework for safe drinking water. The framework includes health-based targets to assist national authorities who are normally responsible to set the targets for the protection of public health from risks by exposure to drinking water. Assessing the adequacy of systems, defining and monitoring control measures, and establishing management plans are the three components of the so-called water safety plans. Achievement of health-based targets may be verified by independent surveillance to assess the safety of the drinking water through additional verification or audit-based approaches. This framework for safe drinking water can be adapted according to environmental, social, economic, and cultural circumstances of drinking water provision on the national, regional, and local level. The chapter concludes that viruses could be considered as biocolloids with specific properties such as size, shape, structure, charge, composition, and genome. These viral characteristics determine their behavior in the environment, resistance to natural inactivation and treatment, and disinfection processes. For each (re-)emerging virus these properties may be known or could be assessed predicting the effectiveness of possible intervention measures for prevention of waterborne disease.

Viruses are a major cause of waterborne and water-related diseases. Extreme examples include the outbreak of hepatitis A and of viral gastroenteritis in Shanghai caused by shellfish harvested from a sewage-polluted estuary. Viruses predominantly associated with waterborne transmission are members of the group of enteric viruses that primarily infect cells of the gastrointestinal tract, and are excreted in the faeces of infected individuals. The viruses concerned are highly host specific, which implies that their presence in water environments is sound evidence of human faecal pollution. In some cases different strains of a viral species, or even different species of a viral genus, may infect animals. The extent of the host specificity of enteric viruses is such that it is used as a valuable tool to distinguish between faecal pollution of human and animal origin, or to identify the origin of faecal pollution. The hepatitis E virus may be the only meaningful exception to this rule, having strains that seem to infect both humans and certain animals, complying with the definition of a zoonosis. The potential risk of infection associated with respiratory viruses such as influenza and severe acute respiratory syndrome in water environments cannot be ignored. However, there is sound reason to believe that treatment and disinfection processes recommended for the acceptable control of enteric viruses will also accommodate enveloped viruses with a substantial safety margin.