Judy Stone, MD
November 17, 2021
A systematic review of studies of infections found no evidence of airborne transmission of respiratory or enteric pathogens in public washrooms, but some experts disagree with the study's conclusions. The study was published in Science of the Total Environment.
Sotiris Vardoulakis, PhD, of the Australian National University, Canberra, Australia, and colleagues reviewed studies of infections associated with public washrooms.
The researchers used keywords to identify potential articles. After screening study abstracts to ensure that only publicly available washrooms with toilets, sinks, and hand dryers were included, 65 studies remained. The investigators excluded washrooms on public transportation (ships, planes, trains, and buses).
"What most of the studies concluded was that what's really important is to have good hand hygiene and proper maintenance and ventilation of washrooms," Vardoulakis told Medscape Medical News in an interview. "So if the hand washing and drying is effective in the first place, it's unlikely that the bathroom air or surfaces will pose an infectious disease transmission risk."
There has been ongoing debate on whether electric hand dryers or paper towels are better. Some studies focused on hygiene. Others focused on the environmental cost of paper towels. One concern is that air dryers might spread germs further.
One study focused on the idea that the air recirculation from electric dryers may spread infective aerosols. Another study determined that the Airblade filters in some electric dryers clean more than 99% of the bacteria. A 2012 review by Cunrui Huang, MMed, MSPH, and colleagues that was published in Mayo Clinic Proceedings concluded that "drying hands thoroughly with single-use, disposable paper towels is the preferred method of hand drying in terms of hand hygiene." Many people prefer to use paper towels because they can be used as a barrier when opening the washroom door.
Vardoulakis dismisses the air-vs-paper debate, saying, "If the hand washing and drying is effective in the first place, it's unlikely that the bathroom air or surfaces will pose an infectious disease transmission risk."
Although Vardoulakis' review did not find that public washrooms pose a risk for infection, other researchers have shown that some settings do pose problems. For example, toilet plumes are thought to have contributed to the 2003 outbreak of severe acute repiratory syndrome at the Amoy Gardens housing complex in Hong Kong and nearby buildings by aerosolization of fecal waste. Also, norovirus has long been shown to be transmitted by aerosolized particles in vomitus or stool.
Rodney E. Rohde, PhD, professor and chair, Clinical Lab Science Program, Texas State University, San Marcos, Texas, expressed concern about this systematic review in an email to Medscape Medical News. "I believe one of the major limitations is that studies which involved restrooms on planes, hotels, camping (those camp kids are nasty), and other similar public-access restrooms MUST be included in this type of review. I also believe they excluded restrooms from low-income/rural areas. WHAT? Their ultimate conclusions seem to be in line with the most current understanding about hand hygiene (including drying without devices that create strong air currents, which may create widespread emission of microbes)."
In an interview with Medscape, Emanuel Goldman, PhD, professor of microbiology, biochemistry, and molecular genetics, Rutgers New Jersey Medical School, Newark, New Jersey, focused on the COVID-specific aspects of the review. "The chances are less than one in 10,000 of getting COVID from a fomite, and that's very conservative," he said. "I think it's a lot lower than that. The virus is fragile. It dies very quickly outside of a human host." He emphasized, "Virtually no infectious virus has been found on fomites over the last two years... A big mistake in a lot of papers is they confuse viral RNA with the virus. It's not the same. Viral RNA is the genetic material of the virus, but it also is the ghost of the virus after the virus is dead, and that's what people are finding. They're finding the ghost of the virus."
Because "studies show that the transfer from a surface to fingers is in the neighborhood of 10% efficiency" and one's fingers also kill the virus, "transmission through your fingers is not easy," Goldman said. "You've got to really work at it to deliberately infect yourself" with COVID from a fomite.
Rohde's conclusion about Vardoulakis's review? "So, the question may be, have there been enough studies, in general, of these other areas to include in a review? Otherwise, can we really generalize from this study? I don't think so."
Goldman is not worried about COVID transmission in public bathrooms. His summation: "I think indoor dining is more risky than anything else right now."
The study was funded by Dyson Technology Ltd. Vardoulakis is a member of the Dyson scientific advisory board.