Water Talk - Enteric viruses in drinking water

Health Canada has updated the guideline for enteric viruses in drinking water to protect the health of Canadians. Learn about the health effects of enteric viruses and how to reduce your exposure from your drinking water.

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Enteric viruses in drinking water

Enteric viruses are the smallest group of microscopic organisms that infect the gut of humans and other mammals and cause illness. They cannot multiply in the environment without a host (human or other mammal), but can survive there for a very long time. There are more than 140 types of enteric viruses that can infect humans.

They can be present in:

Surface water (e.g., rivers and lakes) supplies become contaminated when feces and urine containing enteric viruses are flushed into the water. Because of their small size, enteric viruses can also travel into groundwater supplies through cracks in the ground. Water is only one way in which enteric viruses can be spread; others include person-to-person and food.

Health effects of enteric viruses in drinking water

If there is even just a few enteric viruses in your drinking water, you can get sick. Enteric viruses can cause different health effects depending on the type, and they can be immediate and long-term. Gastrointestinal illness is common and symptoms may include:

If you are suffering from any of these symptoms and think that it is because of enteric viruses, you should consult your healthcare provider and mention any exposure you may have had to water or food that may have been contaminated.

Some enteric viruses can cause more serious illness, such as:

If you have a lowered immune system, for example if you are living with cancer, or if you are a child or an older adult, the illness can be severe. Enteric viruses have been linked to long-term health effects, including diabetes mellitus and chronic fatigue syndrome.

Guideline for enteric viruses in drinking water in Canada

To ensure the safety of drinking water, Health Canada worked with provinces, territories and other federal departments to establish a health-based treatment goal for enteric viruses in drinking water.

The water should be treated to filter or disinfect at least 99.99% of the enteric viruses. Some water supplies will need more than this minimum level of treatment. Most water sources across Canada will have enteric viruses in them.

How to reduce your exposure to enteric viruses in drinking water

If there is reason to believe that enteric viruses are present in a public drinking water supply, an advisory will be put out to the community to boil the water before drinking it. In the case of a disease outbreak, municipal, provincial or territorial authorities will provide more information.

If you have a private well, laboratory tests are not recommended because testing to detect enteric viruses is difficult and expensive. Instead, you should make sure feces and urine do not get into your well water. More information about protecting your well water from contaminants that can make you sick can be found here. Treatment of the water from your well is a good option to reduce your exposure.

If you suspect your water is contaminated by feces, you should boil all water used for:

Under most circumstances, you don't need to boil tap water used for other household purposes, such as bathing, showering, laundry, or washing dishes. Infants, toddlers and immunocompromised individuals should be sponge bathed to reduce the chance of them swallowing any contaminated water.

If you are pregnant or breastfeeding

If you are pregnant or breastfeeding and suspect that your drinking water may contain feces, these same actions will protect your health; you are not at higher risk of becoming ill. However, if you are exposed to enteric viruses and become ill, your symptoms may be more serious.

Removing enteric viruses from drinking water

Provinces and territories regulate municipal drinking water supplies. Consumers don't need any additional treatment for enteric viruses for drinking water supplied by a municipality.

Using water treatment devices

If you have your own well water supply, treatment options for enteric viruses include:

For chlorine disinfection, use hypochlorite solutions that are certified as meeting NSF/ANSI Standard 60 and follow the handling and storage recommendations.

For UV disinfection, look for units that meet NSF/ANSI Standard 55 Class A.

UV disinfection is intended for water that is usually clear (that is, not coloured, cloudy or turbid). If the water is cloudy, it should be filtered first.

Make sure that any device you buy is:

Values in other countries

Health Canada's recommendation of a minimum 99.99% reduction of enteric viruses from the source water is comparable to the United States Environmental Protection Agency's requirement.

The World Health Organization recommends providing control measures within a water safety plan, in order to reduce potential risks from enteric viruses.

For more information

Guidelines for Canadian Drinking Water Quality: Guideline Technical Document - Enteric Viruses.

If you have questions about the guideline, you can contact us at:

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