Toilets dominate environmental detection of SARS-CoV-2 virus in a hospital

Zhen Ding; Hua Qian; Bin Xu; Ying Huang; Te Miao; Hui-Ling Yen; Shenglan Xiao; Lunbiao Cui; Xiaosong Wu; Wei Shao; Yan Song; Li Sha; Lian Zhou; Yan Xu; Baoli Zhu; Yuguo Li

The results suggest that for the Covid-19 patients studied here, the toilet is the most contaminated environment, although the chi-square P value is only 0·064 ( Table 2 ). Our detection of more positive surface samples in the bathroom suggests that these samples may be faecal in origin. The previous detection of the virus in stools 3-5 provides support for this interpretation, as does the fact that stools obtained from the first Covid-19 patient in the United States also tested positive. 7 Zhang et al. 5 also found that there were more anal swab positives than oral swab positives in the later stage of infection, and diarrhoea and nausea prior to fever and dyspnoea also presented in approximately 10% of the patients in Wuhan. 8 High levels of viral load have also been detected in stool in SARS-CoV patients. 9 Our detection of positive surface samples on one toilet ceiling-exhaust grille in a bathroom suggests that fine virus particles existed in that bathroom. However, little is known about the aerosol concentration in the bathrooms in this hospital. Deposition on exhaust grille surfaces can be a result of either long-term deposition of low-concentration particles in the air or fast deposition of high-concentration particles. It has also be confirmed that aerosols may be generated during toilet flushing. 10 A patient's hands can also be contaminated during his/her toilet usage. Toilet bowl and sink surface samples also tested positive in a Singaporean hospital. 11 In addition to toilet flushing-generated aerosols, Yu et al 12 found that SARS-CoV bio-aerosols were generated in drainage stacks after patients flushed the toilet in the 2003 Amoy Garden outbreak.