Hepatitis viruses

(endorsed 2011)

Guideline

No guideline value has been set for Hepatitis viruses and their 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 term hepatitis virus describes a group of viruses that target the liver and cause inflammation. The viruses that cause hepatitis are a functional rather than a genetic group, which have been designated A, B, C etc. Enteric hepatitis viruses including Hepatitis A and E are transmitted by the faecal-oral route and can be transmitted from contaminated food or water. The other types are parenterally transmitted blood-borne viruses that are not transmitted by water.

Hepatitis A is a single-stranded RNA non-enveloped virus from the family Picornaviridae. There is only one known genetic type. It is highly infectious and causes the disease commonly known as “infectious hepatitis”. It enters the body by ingestion, infects epithelial cells and from there passes to the liver via the bloodstream. Like many of the picornaviruses, it causes mild and asymptomatic infections in children but more severe illness in adults. Immunity in adult populations in developing countries may exceed 95%, while it can be less than 50% in developed countries. Hepatitis A is more common in developing countries but has a wide geographic distribution (WHO 2002, 2004)

Hepatitis E is also a single-stranded RNA non-enveloped virus. Classification remains uncertain, but it is not from the family Picornaviridae. There is evidence of genetic variability. It causes hepatitis that is similar in many ways to that caused by Hepatitis A. However, it can have up to a 25% mortality rate in pregnant women. It is widespread but is endemic in regions such as Mexico, Nepal, India, central Asia and parts of Africa, where first infections typically occur in young adults. In these areas Hepatitis E can be the most common source of viral hepatitis. In regions such as North and South America, Japan, Great Britain and Australasia, clinical cases are uncommon and outbreaks rare.

Australian significance

There are about 300-500 cases of Hepatitis A and 10-30 cases of Hepatitis E recorded in Australia each year. There is little information on the occurrence of Hepatitis A or E in Australian drinking water supplies. There have been outbreaks of Hepatitis A in Australia. In 1997, 422 illnesses were caused through consumption of oysters grown in contaminated water at Wallis Lake (Kardamanidis et al. 2009).

Internationally, waterborne outbreaks have been caused by both Hepatitis A and E. In endemic areas, faecally contaminated water can play an important role in transmission of Hepatitis E and large outbreaks involving up to 100,000 people have been reported (WHO 2002, 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 Hepatitis A and E 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 Hepatitis A and E 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 Hepatitis A. 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 Hepatitis viruses; 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 Hepatitis viruses are suspected or known to be present in the raw water, treatment will be required. Hepatitis viruses 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

Incubation periods are relatively long, at 28-30 days for Hepatitis A and 15-60 days for Hepatitis E. Both appear to be highly infective.

Hepatitis A causes “infectious hepatitis”. Infants and young children rarely show symptoms following infection or will only have mild symptoms. Adults experience stronger symptoms including fever, weakness, fatigue, nausea, joint aches, vomiting and jaundice. Duration varies but liver function typically begins to normalise after 30-40 days. Death is rare and is normally associated with pre-existing conditions or people over 50 years of age.

Hepatitis E causes similar symptoms to Hepatitis A but pregnant women are at a greater risk of severe illness and mortality in this group can be up to 25% in endemic areas.

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, 2004). 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

Kardamanidis K, Corbett SJ, Zammit AP (2009). Hepatitis A: Wallis Lake revisited. NSW Public Health Bulletin, 20:29-30.

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) (2002). Enteric hepatitis viruses. In: Guidelines for Drinking-water Quality 2nd Edition, Addendum: Microbiological agents in drinking water. World Health Organization, Geneva, Switzerland.

WHO (World Health Organization) (2004). Guidelines for Drinking-water Quality, Sections 7.2 Health-based target setting, 11.2.5 Hepatitis A and 11.2.6 Hepatitis E. World Health Organization, Geneva, Switzerland.