Detection of SARS-CoV-2 in Exhaled Breath from COVID-19 Patients Ready for Hospital Discharge

Zhou, Lian; Yao, Maosheng; Zhang, Xiang; Hu, Bicheng; Li, Xinyue; Chen, Haoxuan; Zhang, Lu; Liu, Yun; Du, Meng; Sun, Bochao; Jiang, Yunyu; Zhou, Kai; Hong, Jie; Yu, Na; Ding, Zhen; Xu, Yan; Hu, Min; Morawska, Lidia; Grinshpun, Sergey A.; Biswas, Pratim; Flagan, Richard C.; Zhu, Baoli; Liu, Wenqing; Zhang, Yuanhang

The COVID-19 pandemic has brought an unprecedented crisis to the global health sector1. When recovering COVID-19 patients are discharged in accordance with throat or nasal swab protocols using reverse transcription polymerase chain reaction (RT-PCR), the potential risk of re-introducing the infection source to humans and the environment must be resolved 2,3,4. Here we show that 20% of COVID-19 patients, who were ready for a hospital discharge based on current guidelines, had SARS-CoV-2 in their exhaled breath (~105 RNA copies/m3). They were estimated to emit about 1400 RNA copies into the air per minute. Although fewer surface swabs (1.3%, N=318) tested positive, medical equipment frequently contacted by healthcare workers and the work shift floor were contaminated by SARS-CoV-2 in four hospitals in Wuhan. All air samples (N=44) appeared negative likely due to the dilution or inactivation through natural ventilation (1.6-3.3 m/s) and applied disinfection. Despite the low risk of cross environmental contamination in the studied hospitals, there is a critical need for strengthening the hospital discharge standards in preventing re-emergence of COVID-19 spread.