UCI analyzes bathroom transmission of virus

April 10, 2020

By Anna Lynn Sptizer and Lori Brandt

To date, the U.S. Centers for Disease Control and Prevention and other health agencies have believed the coronavirus’s primary route of transmission is through large respiratory droplets emitted in a cough or sneeze. But transmission is not fully understood, and scientists are debating whether the novel coronavirus can spread through the air. 

UCI civil engineering and environmental researchers are investigating the risks of exposure to the virus through contaminated aerosols in the bathroom. According to Sunny Jiang, professor of civil and environmental engineering, researchers in Wuhan, China, detected live SARS-CoV-2 in patients’ feces, raising concerns of possible transmission through aerosols generated from the toilet or drains connected with the building sewer pipe in multi-unit buildings, such as apartments or hospitals. 

Her team conducted a quantitative microbial risk assessment to estimate the health risks associated with two aerosol exposure scenarios: toilet flushing and faulty drainage/sewage plumbing. SARS-CoV-2 data were collected from the rapidly emerging literature. The human exposure dose was calculated using a simulation of viral concentrations in aerosols under each scenario and human breathing rates. 

Jiang says the results indicate the median risks of developing COVID-19 are generally low for both scenarios. However, the worst-case scenario from using a documented SARS-CoV-2 concentration in aerosols of hospital toilet rooms showed a risk of over one in 1,000 chance. The research has been submitted for publication in Environmental Science and Technology. Jiang and graduate student Hunter Quon worked with environmental researchers Kuangwei Shi, Zi-Lu Ou-Yang and Chengwen Wang from Tsinghua University in Beijing China.