Norvirus-Get Ready

What Cleaners Kill Norovirus on Surfaces?

Norovirus, aka Norwalk, is in the news again. It’s sometimes called “stomach flu” but has nothing to do with any influenza virus. It does, however, deliver some nasty symptoms above and beyond your standard winter cold. There are no vaccines or antibiotics that can prevent or relieve symptoms but you can reduce your chances of catching it.

What Cleaners Kill Norovirus?

Virtually any standard sanitizer including hydrogen peroxide, quat (quaternary ammonium chloride) or chlorine bleach can kill norovirus. Of these, chlorine bleach is cheap & readily available.

How Long Does Norovirus
Live on Surfaces?

Norovirus can survive up to 2 weeks on surfaces such as doorknobs, laundry and handrails.  Disinfection of most viruses require levels in the 500-800ppm range. So, why does the CDC (1) recommend 1000-5000ppm for norovirus?

The problem is that Norwalk virus mixed in with vomit and diarrhea remains active even after a floor has been mopped “clean”. Bleach is taken up by any organic matter and since viruses are very small most of the bleach is absorbed by the unseen vomit/diarrhea.  By preparing a 5000ppm concentration, you insures that the virus is ultimately exposed to something that is at least 1000ppm.

Preparing Bleach for Sprayers

The CDC (1) instructions for 1000–5000 ppm say to use 5–25 tablespoons of household bleach [5.25%] per US gallon of water. In metric this is ~75 to 375ml per 4L.

Hospitals and other healthcare facilities have to deal with worst case scenarios so higher strengths and greater volume of bleach mixture is required. Daycare or nursing homes may only need to prepare enough for small spray bottles, a cup/250ml is usually enough.

Measure & Test Bleach Strength Accurately for Effective Norovirus Disinfection.
For 1000ppm, add 1 tsp/5ml of bleach to make up a cup/250ml.   For 5000ppm, add 5tsp/25ml of bleach. Increase this by 4 to make a quart/litre; 16 times  for a gallon/4L.

If you want to do different concentrations or volumes, you can use our Sanitizer Dilution Calculator. It works in metric units but we list nearest American equivalents as well.

Which Test Strip to Use for Norwalk?

Health and safety inspectors will generally insist you test your solutions for dilution accuracy. This is because it is possible to make mistakes and it also adds a further check in case your bleach strength isn’t at the most common level of 5.25%.

33815-10Kppm-Cl-Color-Chart
Use this versatile chlorine test strip to confirm you disinfection solutions for norovirus (Norwalk) are at the right concentrations.

We recommend our 0-10,000 (10K) chlorine test strip for this. The color chart has markings for 1000, 2500 & 5000ppm so this one strip can be used for all the concentrations mentioned above.

References

  1. CDC: Norovirus, Preventing Infection
  2. City of Toronto: Norovirus Fact Sheet
  3. How to clean up after a Norovirus Outbreak. Includes a very informative audio.
  4.  Norovirus in kids: How to prevent it, and how to cope when that fails.

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