By Dr. Jay Glasel
"Aerosol: Particles, either liquid or solid, suspended in air" – Definition from the Textbook of Military Medicine, Part I: Medical Aspects of Chemical and Biological Warfare
It's with good reason that the most effective delivery method for biological warfare weapons is via aerosol suspensions: finely divided droplets or powders containing bacteria may be carried by air currents for long distances spreading their contamination as they are inhaled or fall on surfaces to be picked up later by touch. Also, the aerosol droplets are so small (diameters less than 0.0002 inches) that they can't be seen by the naked eye without special lighting effects and so the spread of contamination can't be easily detected.
When humans sneeze they produce biological warfare weapons of their own: aerosols containing aqueous droplets enriched with a wide variety of the bacteria found in all human respiratory systems. The aerosol droplets are about the same size as those used for biowarfare.
Most people have enough sense not to sneeze without covering their nose and mouth briefly. But in restrooms there's another source of powerful biowarfare weaponry that is not recognized by many people.
From pioneering work done by microbiologists nearly 50 years ago, it has been known that flushing of many types of toilets produces bacteria-bearing aerosols with droplet sizes closely approximating those from human sneezes and military bioweapons. It's natural that this has been given the unappetizing name of "toilet sneeze". The original microbiological results were extended in a scientific paper  that showed that within 2 hours after a single flush of this type of toilet in a 36 ft2 restroom, bacteria could be found randomly distributed throughout the restroom surfaces. That is, the bacteria-containing aerosol droplets from toilet sneeze remain airborne for relatively long times before coming to rest on—and contaminating—both horizontal and vertical surfaces. Unless removed immediately, and that is almost never done, the fallen aerosol droplets from toilet sneeze dry on the surfaces. 
Recently, it has also been shown by microbiologists that bacteria found dried on surfaces may remain viable (that is, can still be infectious) for days, weeks, and even months after they have been deposited on the surfaces by aerosols such as those from toilet sneeze. Also, dried bacteria on surfaces may be picked up by air currents and vibrations and become re-aerosolized as infectious particles in restroom air.
Since human solid waste is known to contain many hundreds of different species of bacteria, many of them pathogens (species that cause disease in humans and animals), toilet sneeze is a very efficient way of spreading potentially dangerous bacterial contamination all over restrooms, especially in multi-stall public restrooms. Unless removed efficiently or killed by disinfection, the bacteria in the dried aerosols may remain viable for a long time.
The question is how can this toilet sneeze-caused contamination be minimized?
While there are toilet devices that have mesh covers that minimize aerosol production when put down before flushing (and just putting the seat cover down before flushing cuts down on toilet sneeze) the fact is that just a few flushes where this is not done will serve to contaminate a restroom. So, the only currently available solution to minimize toilet sneeze-caused contamination is adequate restroom cleaning.
The only adequate bacterial mitigation procedure is one that ensures with quantitative post-cleaning data that contamination has actually been removed to a desirable level. That is, an adequate procedure is one that integrates cleaning, disinfection, and microbiological measurement. Integration of a cleaning process with measurement of the microbiological outcome of the process is the basis of one part of the concept of ICM (Integrated Cleaning and Measurement) that has recently been introduced to the cleaning industry.
No-touch spray-and-vac systems include disinfectant metering and injection in a pressure washer with a vacuum system specifically targeted at restroom cleaning. When used with a rapid organic material/bacterial detection instrument such as a palm-sized ATP device, the combination forms a powerful ICM process. An additional advantage of this bio-pollutant detection system is that the data collected can be stored in a computer to form part of a permanent record of cleaning efficiency.
Efficiently removing dried bacterial contamination from tiled public restroom floors with grouted joints is an especially difficult task because the contamination enjoys the protection of the rough grout surfaces. However, it has been quantitatively shown that the spray-and-vac process where fresh cleaning and disinfecting solution is continuously applied to tiled bathroom surfaces and subsequently extracted into a waste container is at least 60 times more effective in reducing bacterial contamination from grouted tile restroom floors than conventional wetting and wringing cleaning cycles .
The phenomenon of toilet sneeze and the lingering contamination it can cause in restrooms needs to be more fully recognized by the cleaning industry along with the advantages of implementing the ICM model to meet this contamination challenge.
 Gerba, C.P., Wallis, C., Melnik, J.L. (1975) Microbiological Hazards of Household Toilets: Droplet Production and the Fate of Residual Organisms, Appl. Microbiol. 30 229-237.
 Glasel, J.A. (2008) Cleaning Methods for Ceramic Tile Floors, Cont. Environ. 11 19-22.
Author: Jay Glasel PhD
Dr. Glasel is the Managing Member and Founder of Global Scientific Consulting, LLC. He is a Professor Emeritus in the Department of Microbial, Molecular and Structural Biology at the University of Connecticut Medical/Dental School in Farmington, Connecticut. He has lectured and done research in many countries in Europe and Asia.
Dr. Glasel's scientific research has been in the fields of structural biochemistry, molecular immunology, pharmacology, and cell biology. Major portions of the research involved the structure and properties of water and aqueous solutions and on the structural chemistry and molecular biology of opiates and opiate peptides. He pioneered the uses of anti-morphine monoclonal antibodies and anti-opiate receptor anti-idiotypic antibodies in research on the cellular effects and actions of narcotics.
Dr. Glasel is co-editor and an author for the Academic Press textbook "Introduction to Biophysical Methods for Protein and Nucleic Acid Research" and many other contributed book chapters and original scientific research articles.
Dr. Glasel obtained a B.S. in chemistry and physics from Caltech. His Ph.D. from the University of Chicago was in chemical physics for work on chemical reactions on comets. He has served on active duty in the U.S. Air Force as a nuclear research officer.