Recent data from the Centers for Disease Control and Prevention indicate that approximately 25% of infected patients may not have clinical signs or symptoms, meaning gastrointestinal (GI) or the classic respiratory illness, but may still be viral shedders. A percentage of patients with an asymptomatic prelude may also have viral shedding for about 2 to 3 days before they then develop the more classic respiratory illness.
In light of the puzzling nature of this epidemiologic spread, we've adapted social distancing. However, I want to talk about one other potential means of its spread: the toilet.
As we know, GI diseases can be transmitted via the fecal-oral route. Now researchers looking at hospitals in Wuhan, China, that treated COVID-19-positive patients have provided valuable new data on its transmission. They found that although the intensive care units were good at containing the spread of the virus outside of the patients' rooms, there was a high concentration of the virus in the air samples taken from the patients' toilets.
What are the implications of that finding? Droplets of SARS-CoV-2, which causes the disease COVID-19, can be spread and live in the air for up to 3 hours, and be disseminated to hard surface areas where they can live up to 3 to 4 days. That is quite concerning when you consider that flushing a toilet can create an aerosolized plume of these viral particles, which can then spread elsewhere within proximity. We know that toothbrushes left in proximity to the toilet gain viral spread quite rapidly, mirroring levels observed in the toilet itself. That same thing can occur for cell phones, which many people take with them into the bathroom. However, this mode of transmission has not been well studied as it relates to COVID-19.
We do have available evidence with another coronavirus, the severe acute respiratory syndrome (SARS). Researchers looked at the Amoy Gardens apartment complex in Hong Kong, which experienced a large community outbreak of SARS during the 2003 epidemic. Using airflow dynamics studies, they were able to retrospectively track the spread of the virus from one individual patient—the index case—to other residents of the complex. They reported that the patient's toilet exhaust fan, which created a negative pressure effect, vented into the apartments above and also to the outside. They linked this to 187 cases in the complex with available data. This analysis suggests that the SARS virus was able to be transmitted by microdroplets through inhalation, touch, and potentially fecal-oral routes.
We can and should practice social distancing, taking a step back so we're 6 feet away from each other. But what do we do to address concerns that the toilet microbiome may put us at risk for COVID-19?
Certainly, hospitals caring for these patients need to pay close attention to toilet cleansing and determine whether there are venting systems that expel air from the toilet via a negative pressure effect. It also raises questions about the use of toilets in the public domain. Six-feet social distancing means I can see you, you can see me, and we can stay apart. But if I use a toilet, there's no way of knowing whether it was used prior by a symptomatic or asymptomatic viral carrier or shedder.
The aerosolization effect that can occur in toilets, leading to microdroplets that can be inhaled or persist on surface areas, raises some real concerns regarding epidemiologic spread. It may also be helpful in understanding why this rapid spread can occur when not linked to known contact with those positive for COVID-19.
Turning our attention to the toilets is something we need to do. It's very prudent for those caring for patients in the hospital. And for those who are out of the hospital and trying to stay healthy, consider avoiding public-domain toilets.
We don't have the answers yet, but there are some evidence-based steps that I encourage you to consider.
David A. Johnson, MD, a regular contributor to Medscape, is professor of medicine and chief of gastroenterology at Eastern Virginia Medical School in Norfolk, Virginia, and a past president of the American College of Gastroenterology. His primary focus is the clinical practice of gastroenterology. He has published extensively in the internal medicine/gastroenterology literature, with principal research interests in esophageal and colon disease, and more recently in sleep and microbiome effects on gastrointestinal health and disease.