Enterovirus

(endorsed 2011)

Guideline

No guideline value has been set for Enterovirus and its inclusion in routine monitoring programs is not recommended.

A multiple barrier approach from catchment to tap is recommended to minimise the risk of contamination. Protecting catchments from human and animal wastes is a priority. Operation of barriers should be monitored to ensure effectiveness and that microbial health-based targets are being met.

General description

The genus Enterovirus is in the family Picornaviridae. They are among the smallest of the viruses with a diameter of 20-30nm and consist of a single-stranded RNA genome in a non-enveloped capsid. The genus includes a broad range of serotypes that infect humans including polioviruses, coxsackieviruses, echoviruses and enteroviruses. Enteroviruses have a worldwide distribution. In temperate climates, most major epidemics occur during the later summer months, whereas in the tropics, disease can occur throughout the year.

Enteroviruses are one of the most common causes of human infections and can cause a broad range of symptomatic infections. Transmission is mainly by person-to-person contact and inhalation of aerosols. Transmission from contaminated drinking water is plausible but has not been proven (WHO, 2004).

Australian significance

Enterovirus infections are common in Australia but there is little information on the occurrence of these viruses in Australian drinking water supplies.

Internationally, enteroviruses have been detected in source waters and drinking water supplies (Grabow et al. 2001).

Method of identification and detection

Detection of enteroviruses in water typically requires concentration from large volumes of water (10–1000 litres depending on the source). The concentrate is then inoculated into cell cultures. The presence of infectious enteroviruses can also be detected by cytopathic effects with enumeration determined using dilution series. Alternatively, a plaque-forming assay can be used.

The presence of the virus can also be determined by PCR-based analyses. A limitation of PCR-based methods is that they do not measure infectivity.

Preventing contamination of drinking water

A multiple barrier approach operating from catchment to tap should be used to minimise the risk of contamination. Human faecal waste is the source of infectious enteroviruses in water supplies, and protection of water catchments from contamination by human wastes is a priority.

Water from catchments receiving human waste is likely to be susceptible to contamination with enteroviruses, and treatment, including effective filtration and disinfection, will be required to ensure a safe supply. The lower the quality of source water, the greater the reliance on water treatment processes.

Sanitary surveys of water catchments should be undertaken to identify potential sources of human waste, assess risk factors for contamination, provide a basis for catchment management to reduce these risks, and determine the level of water treatment required.

Groundwater from confined aquifers or from depth is not generally subject to contamination by enteroviruses; however, bores need to be well maintained and protected from intrusion of surface and subsurface contamination. Integrity should be monitored using traditional indicators of faecal contamination.

Where enteroviruses are suspected or known to be present in the raw water, treatment will be required. Enteroviruses are sensitive to disinfection using agents such as chlorine and UV light. Media filtration (with coagulation) and membrane filtration can reduce concentrations by 90% or more depending on membrane pore size and effectiveness of operation. Filtration plants should be operated by trained and skilled personnel.

The integrity of distribution systems should be maintained. Backflow prevention policies should be applied and faults and burst mains should be repaired in a way that will prevent contamination.

Health considerations

The genus Enterovirus includes a broad range of serotypes that can cause human infections. These serotypes collectively cause a spectrum of diseases including mild febrile illness, myocarditis, meningoencephalitis, poliomyelitis, hand-foot-and-mouth disease and neonatal multi-organ failure. However, most infections are asymptomatic.

Derivation of guideline

The infectious dose for many viruses is very low (1-10 particles) and risk assessments have indicated that safe drinking water should contain less than 1 virus particle per 1000 litres of water (Regli et al. 1991, WHO 2006). No guideline value is proposed and inclusion in routine verification monitoring programs is not recommended. The focus should be on monitoring of control measures, including prevention of source water contamination by human waste, effective disinfection, and protection of distribution systems from ingress of faecal material.

References

Grabow WOK, Taylor MB and de Villiers JC (2001). New methods for the detection of viruses: call for review of drinking water quality guidelines. Water Science and Technology 43:1-8.

Regli S, Rose JB, Haas CN, Gerba CP (1991). Modelling the risk from Giardia and viruses in drinking water. Journal of the American Water Works Association, 83:76-84.

WHO (World Health Organization) (2004). Guidelines for Drinking-water Quality, Sections 7.2 Health-based target setting and 11.2.4, Enteroviruses. World Health Organization, Geneva, Switzerland.