Log reductions and Virus Control

August 19, 2020 2 min read

Log reductions and Virus Control

When discussing infection control ‘log reductions’ refers to how effective a product is at reducing pathogens. The larger the reduction, the better the product is as reducing the number of pathogens that could be causing infection and sickness.

The terminology comes from the mathematical term logarithm, which is another way to denote numbers. For example, if 10 is the given number, a log 4 increase can be written as 104 or 10 x 10 x 10 x10 – 10,000. A reduction will go in the opposite direction, meaning a log 1 reduction is a 10-fold reduction or, moving the decimal place one step down, or a 90% reduction.

 In a microbiology context, when counting pathogen colonies, you are counting very large numbers, applying and testing the efficiency of various disinfectant products, then recounting the colonies present. If the product was successful at killing the present pathogens, you would report it as the log reduction:

Log Reduction

Percentage Reduction

Times Smaller























This highlights how important those extra decimal points are when shopping for cleaning products. When discussing viruses, bacteria and other pathogens, the numbers present on a surface is huge. If there are 1 billion bacteria on a dirty surface, and the disinfectant product was capable of a Log3 reduction, or 99.9%, that would mean there would still be 1,000,000 bacteria left on that surface, compared with 1,000 with a 99.9999% reduction. Using a product with a Log6 reduction will leave significantly fewer on your countertop than a product that is categorised as Log3, that 0.0999% will make a big difference in ensuring cleanliness and safety.

Leave a comment

Comments will be approved before showing up.

Also in Stay Safe Blog

Summer is approaching
Summer is approaching

May 17, 2021 1 min read

As we approach the lifting of many restrictions we can look forward to sharing the things we’ve missed most with those we love to be with. If you need a reminder of the changes being made for the next few weeks always check the government website.

Seasonal Behaviours of Infectious Diseases
Seasonal Behaviours of Infectious Diseases

May 09, 2021 2 min read

We often seeing increases in diseases according to seasonal changes. Some examples of this include the annual cycle of flu that often happens as people come together at the start of term in education environments.

Will our behaviour have changed forever?
Will our behaviour have changed forever?

April 30, 2021 2 min read

his is a question we’ve all considered recently. Will things ever be the same again? Or are some of our behaviours and experiences changed forever?

Sign-Up - Exclusive Offers