Is Disinfection Necessary?

Is Household Disinfection Necessary?

By Benjamin Tanner, Ph.D - President, Antimicrobial Test Laboratories

One of the most common questions microbiologists hear is "Surface disinfection, is it really necessary?" The article that follows briefly outlines of the evidence base supporting the use of disinfectants to reduce illness rates in the households.

There is a balance to be struck, however, between the chemical toxicity of disinfectants and their ability to reduce a person's risk of infection by killing germs on surfaces.

How does a microbiologist decide if disinfection is worth it?

A good scientist decides if disinfection is worth it on the basis of empirical evidence - real life observations and studies. That's not to say there's no place for opinions in the life of a scientist, just that when it comes important decisions like "Should I disinfect surfaces at home?" deference should be given to data over opinion. After all, anybody can theorize at whim. Examination of data from past disinfection is the most realiable means to predict the impact of future disinfection.

Hundreds of studies have been done over the years assessing the value of disinfection in one way or another. They can be broken into two basic types: Epidemiological or "disease outcome" studies, and studies that assessed germ levels on surfaces before and after disinfection.

Obviously the most compelling evidence in support of or against disinfection would come from studies observing disease reduction after the implementation of a good disinfection routine. One problem with those types of studies is that infectious diseases can be transmitted by a great number of routes - only some of which are addressed by surface disinfection. Another problem is getting studied populations to comply with the disinfection regimen under study. Still another problem lies in the differences between microbial influx between households and the immunological preparedness of the population under study. As a result of all this complexity, results of observational studies range widely.

There is an economic reality that comes from the inherent complexity of such observational studies of disinfection: A great big, well conducted, objective study of household disinfection would require a large study population be really, really expensive and take a long time!

Not surprisingly, the most common study type available for consideration is a "swab" type of study, where levels of microorganisms on surfaces are determined before and after surface disinfection. These studies typically yield a "percent reduction" of germs on surfaces. Then, by relying on theories that have proven to be reasonably predictive, such as dose-response relationships and transfer rates of germs from surfaces to hands and from the hands to the mouth, microbiologists can estimate the impact such "percent reductions" has on infection rates.

Studies that center on microbiological data, or "swab" studes, are a less direct measurement of the linkage between disinfection and disease, but there are many more of them to consider.

Brief review of studies without microbiological data (epidemiological studies)