Noroviruses and Drinking Water from Private Wells

What are noroviruses (Norwalk-like viruses)?

Norovirus is the official name for a group of viruses previously described as "Norwalk-like viruses" (NLV). Noroviruses cause intestinal illness, or gastroenteritis, and have been associated with outbreaks on cruise ships and in communities, restaurants, camps, schools, institutions, and families.

For more information about norovirus illness and treatment, please visit CDC's norovirus website.

Where and how do noroviruses get into drinking water?

Noroviruses are found in every part of the United States and throughout the world. Noroviruses may be found in water sources, such as private wells, that have been contaminated with the feces of infected humans. Waste can enter the water through various ways, including sewage overflows, sewage systems that are not working properly, and polluted storm water runoff. Wells may be more vulnerable to such contamination after flooding, particularly if the wells are shallow, have been dug or bored, or have been submerged by floodwater for long periods of time.

How can I find out whether there are noroviruses in my drinking water?

If you suspect a problem and your drinking water comes from a private well, you may contact your state certification officer for a list of laboratories in your area that will perform tests on drinking water for a fee.

How do I remove noroviruses from my drinking water?

To kill or inactivate noroviruses, bring your water to a rolling boil for one minute (at elevations above 6,500 feet, boil for three minutes) Water should then be allowed to cool, stored in a clean sanitized container with a tight cover, and refrigerated. Because of the small size of the virus, using a point-of-use filter will not remove it from your water.

You may also disinfect your well. Note that noroviruses are moderately tolerant to chlorination, so you should contact your local health department for recommended procedures. Remember to have your well water tested regularly, at least once a year, after disinfection to make sure the problem does not recur.