Adenovirus
(endorsed 2011)
Guideline
No guideline value has been set for Adenovirus 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 wastes is a priority. Operation of barriers should be monitored to ensure effectiveness and that microbial health-based targets are being met.
General description
Adenoviruses have a DNA genome in a non-enveloped icosahedral capsid. They are widespread in nature and different species cause infections in birds, mammals and amphibians. However, they are not considered a cause of zoonotic transmission. There are six subgenera of human Adenoviruses (A-F) containing about 50 serotypes in total. Subgroup F is the only one of the 6 subgenera that does not grow well in culture.
Adenoviruses cause a wide range of symptomatic infections and can be transmitted by a number of routes including, faecal-oral, hand-eye and inhalation of aerosols. Person-to-person contact plays a major role in transmission and epidemics of acute respiratory and ocular disease have been reported in closed communities such as boarding schools and military camps. Contaminated food and water may also be significant sources and a number of outbreaks involving conjunctivitis and pharyngitis have been reported in association with recreational water exposure.
Adenoviruses cause up to 5% of febrile illnesses in children and also cause a high prevalence of asymptomatic infections (Mena and Gerba 2008). Serotypes that can potentially cause respiratory and other non-enteric infections are commonly detected in faecal material.
Australian significance
There have been limited surveys of Adenovirus in Australian drinking water but they have been detected in sewage (NRMMC, EPHC, AHMC 2006). There have been no reported outbreaks associated with Australian drinking water supplies.
Internationally several large outbreaks of pharyngitis and conjunctivitis have been associated with swimming pools (Foy et al. 1968, Cabelli 1978, Di Angelo et al. 1979, Mena and Gerba 2008). While transmission via drinking water is plausible, it has not been confirmed (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). The concentrate is then inoculated into cell cultures. The presence of infectious Adenovirus can be detected by cytopathic effects with enumeration determined using dilution series.
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 human infectious Adenoviruses 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, 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 wastes, 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 adenoviruses; 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 adenoviruses are suspected or known to be present in the raw water, treatment will be required. Adenoviruses are relatively resistant to UV light and the dose required for a 90% (1 ) kill is (Mena and Gerba 2008). Other disinfectants such as chlorine are more effective. 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
Adenoviruses cause a wide spectrum of symptoms including gastroenteritis, acute respiratory diseases, pneumonia, urethritis, haemorrhagic cystitis, epidemic keratoconjunctivitis (“shipyard eye”) and pharyngoconjunctival fever (“swimming pool conjunctivitis”). Different serotypes are associated with specific illnesses; for example, types 40 and 41 are the main cause of enteric illness. Adenoviruses are an important source of childhood gastroenteritis.
High attack rates in outbreaks imply that infecting doses are very low and this has been confirmed by quantitative risk assessment (Mena and Gerba 2008).
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 Adenovirus per 1000 litres of water (Mena and Gerba 2008). 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
Cabelli VJ (1978). Swimming associated disease outbreaks. Journal Water Pollution Control Federation, 50:1374–1377.
Di Angelo LJ, Hierholzer JC, Keenlyside RA, Anderson LJ, Martone WJ (1979). Pharyngoconjunctival fever caused by Adenovirus type 4: report of a swimming pool outbreak with recovery of virus from pool water. Journal of Infectious Diseases, 140:42–47.
Foy HM, Cooney MK, Hatlen JB (1968). Adenovirus type 3 epidemic associated with intermittent chlorination of a swimming pool. Archives on Environmental Health, 17:795–802.
Mena KD, Gerba CP (2008). Waterborne Adenovirus. Reviews of Environmental Contamination and Toxicology, 198:133-167.
NRMMC (Natural Resource Management Ministerial Council), EPHC (Environment Protection and Heritage Council), AHMC (Australian Health Ministers’ Conference) (2006). Australian Guidelines for Water Recycling: Managing Health and Environmental Risks (Phase 1). Canberra.
WHO (World Health Organization) (2004). Guidelines for Drinking-water Quality, Section 11.2.1, Adenoviruses. World Health Organization, Geneva, Switzerland.
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