Rotavirus

(endorsed 2011)

Guideline

No guideline value has been set for Rotavirus 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.

General description

Rotaviruses are in the family Reoviridae and consist of a double-stranded RNA genome in a non-enveloped capsid. The genus Rotavirus is divided into seven groups, A to G. Group A contain the most important human pathogens.

Rotaviruses are the most common cause of severe diarrhoea among young children. Approximately 50-60% of acute gastroenteritis leading to hospitalisation of children is caused by Rotavirus and it causes over 600,000 deaths each year. Rates of infection are lower in adults and disease tends to be milder. The primary mode of transmission is faecal-oral, with inhalation of aerosols also possible. Although large numbers of particles are excreted by infected people, water plays a smaller role than expected.

Investigations of Rotavirus occurrence have been hampered by the lack of a culture-based assay. Rotavirus can be detected using electron microscopy and PCR-based methods.

Australian significance

Rotavirus infections are very common in Australia and all children are likely to have been infected at least once. There is little information on the occurrence of Rotavirus in Australian drinking water supplies.

Internationally, Rotavirus has been detected in sewage and surface water (Percival et al. 2004, Lodder and de Roda Husman 2005) and occasionally has been associated with waterborne outbreaks (WHO 2004).

Method of identification and detection

Detection of viruses in water typically requires concentration from large volumes of water (10-1000 litres depending on the source). Assays for Rotavirus are based on PCR techniques. 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 Rotavirus 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 Rotavirus, 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 Rotavirus; 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 rotaviruses are suspected or known to be present in the raw water, treatment will be required. Rotaviruses 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 onset of Rotavirus symptoms is usually sudden, with vomiting, watery diarrhoea, and fever. The diarrhoea usually last 2-5 days and, in severe cases, can lead to dehydration. In developed countries such as Australia death is uncommon.

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 (Gerba et al. 1996). 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

Gerba CP (1996). Waterborne rotavirus: a risk assessment. Water Research 30:2929-2940.

Lodder WJ, de Roda Husman AM (2005). Presence of Noroviruses and other enteric viruses in sewage and surface waters in The Netherlands. Applied and Environmental Microbiology, 71:1453–1461.

Percival S, Chalmers R, Embrey M, Hunter P, Sellwood J, Wyn Jones P (2004). Microbiology of Waterborne Diseases. Elsevier Academic Press.

WHO (World Health Organization) (2004). Guidelines for Drinking-water Quality, Section 11.2.7, Rotaviruses and orthoreoviruses. World Health Organization, Geneva, Switzerland.