Apparently they do. According to two studies, toilets “sneeze” when flushed, spewing aerosolized plumes of moisture, bacteria and viruses over many bathroom surfaces. The first study, conducted in 1975 and ominously entitled “Microbiological Hazards of Household Toilets,” showed that this menacing sneeze produced a cloud that stayed airborne for up to two hours and traveled six to eight feet up and out from the toilet. The head researcher (no pun intended), environmental microbiologist Dr. Charles Gerba, had two main recommendations for worried flushers: keep your toothbrush inside a cabinet and close the toilet lid before flushing (finally, a scientific reason to close the lid!).
It took thirty years for a follow up study, but in 2005 researchers confirmed the plume and discovered how it was formed inside the toilet. Unfortunately, they had some bad news for those who thought closing the lid would eliminate the threat. Because of gaps between the lid, seat and rim, the same amount of bacteria escaped whether the lid was open or closed. Luckily, a closed lid does seem to buy flushers a little time to wash their hands. You see, the greatest aerosol dispersal occurs when the water from the flush meets the water in the bowl, so closing the lid and leaving the area immediately after flushing keeps airborne particles from landing on you or being inhaled.

The good news is that normal toilet use is unlikely to present a great health risk. Normal “formed” stool is quickly washed down the toilet, limiting the number of bacterial aerosols that can be created as a result. Health problems are more likely to arise when the toilet is flushed after acute episodes of diarrhea or vomiting.

If you’d like to see the effects of a sneezing toilet, put some food dye into the toilet water, flush it, and hold a piece of white paper horizontally across the seat of the toilet.

And to reduce the chances of a sneezing toilet giving you or your family a cold (or worse), keep in mind these practical tips:

1. Put the lid down before flushing to buy some extra time.
2. Clean your toilet immediately if a user has vomited or had diarrhea. 
3. Clean your toilet regularly. When rings build up in the bowl and under the rim, bacteria and viruses can adhere to them and be ejected during flushing. 
4. Don’t forget to clean the underside of the lid, seat and rim, which are in the direct line of the germy toilet plume.
5. Use an acid cleaner inside the bowl to remove build-up and kill germs. Use a disinfectant cleaner on the rest of your toilet, not just an all-purpose cleaner.
6. Clean from the least contaminated area to the most, then spray and let the disinfectant chemical dwell for the recommended time before wiping. This extra contact time after cleaning is a very effective way to kill bacteria and viruses.
7. Don’t forget that ceilings and walls are impacted too, so be sure to clean these areas every once in a while, especially those nearest the toilet.