Introduction

In December 2019, a novel pneumonia named coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), emerged in Wuhan, China, and has since spread to 25 countries. Current reports show that SARS-CoV-2 is closely related to severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV)1,2 and that it has a greater transmissibility than other coronaviruses. The confirmed transmission modes of SARS-CoV-2 include respiratory droplets and physical contact, and the incubation period for the virus is approximately 3 to 7 days, but it can be as long as 24 days.3 In this case series, we report a cluster-spreading event in Huai’an (700 km northeast of Wuhan) in Jiangsu Province, China, in which a patient with SARS-CoV-2 may have transmitted the virus to 8 other healthy individuals via bathing in a public bath center.

Methods

Data were collected from Huai’an No. 4 Hospital of Jiangsu Province, China. A total of 9 patients who had been to the same bath center were hospitalized and enrolled from January 25, 2020, to February 10, 2020. Throat swab samples were collected, and SARS-CoV-2 was detected using a quantitative reverse transcription–polymerase chain reaction assay. Computed tomography and hematological examinations were performed for auxiliary diagnoses. Data were analyzed with Prism version 7.00 (GraphPad). This study was approved by the ethics committee of Huai’an No. 4 Hospital, and written informed consent was obtained from all patients. This study followed the reporting guideline for case series. No prespecified threshold for statistical significance was set.

Results

The bath center for men was approximately 300 m2, with temperatures from 25 to 41 °C and humidity of approximately 60%. It contained a swimming pool, showers, and sauna. The first patient (patient 1) had traveled to Wuhan. He went to the bath center and showered on January 18, 2020. He started experiencing a fever on January 19, 2020, and was diagnosed with COVID-19 on January 25, 2020. The next 7 patients showered, used the sauna, and swam in the same center on January 19 (patients 2, 3, and 4), January 20 (patient 5), January 23 (patients 6 and 7), and January 24 (patient 8). The symptoms associated with COVID-19, including fever, cough, headache, and chest congestion, appeared between 6 and 9 days after visiting the bath center. Patient 9 was working in the bath center and experienced onset on January 30. Infection in all patients was confirmed by positive reverse transcription–polymerase chain reaction assay results (Figure).

The median (interquartile range) age of the patients was 35 (24-50) years. A total of 8 patients (89%) reported fever (mean [SD] duration, 5.78 [2.99] days), and 7 patients (78%) reported a cough. Few patients (3 [33%]) showed debilitation, chest distress (2 [22%]), or anorexia (1 [11%]). Diarrhea, myalgia, rhinorrhea, and headache were not reported. C-reactive protein levels were elevated in 9 patients (100%; mean [SD], 3.34 [3.18] mg/dL; to convert to milligrams per liter, multiply by 10). Lymphopenia occurred in 3 patients (33%), lactate dehydrogenase was increased in 3 patients (33%; mean [SD], 225.56 [85.33] U/L; to convert to microkatals per liter, multiply by 0.0167), and glutamic oxaloacetic transaminase was increased in 2 patients (22%; mean [SD], 30.22 [13.94] U/L) (Table).

Computed tomography examinations were performed, and the ground glass opacities were observed in all 9 patients. As of February 10, 2020, no patients required respiratory support.

Discussion

Previous studies have demonstrated that the transmission rate of a virus is significantly weakened in an environment with high temperature and humidity.4 However, judging from the results of this study, the transmissibility of SARS-CoV-2 showed no signs of weakening in warm and humid conditions. We noticed a clustered case occurring in a public bath center with high temperature and humidity. A total of 8 individuals who used or worked in the bath center experienced symptoms within 6 to 9 days of their visit to the center, suggesting that SARS-CoV-2 could spread and cause infection in such an environment. The transmission routes may also be respiratory droplets or contact, but our results suggest that the cluster transmission of SARS-CoV-2 can still arise in an environment with high temperature and humidity. These results provide a potential epidemiological clue for this novel coronavirus. This study was limited by a lack of detail regarding the transmission routes of the patients in the bath center.

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Accepted for Publication: March 6, 2020.

Published: March 30, 2020. doi:10.1001/jamanetworkopen.2020.4583

Correction: This article was corrected on August 5, 2020, to fix an error in Funding/Support.

Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2020 Luo C et al. JAMA Network Open.

Corresponding Authors: Qilong Wang, MD, PhD, Department of Central Laboratory, The Affiliated Huai’an No. 1 People’s Hospital, Nanjing Medical University, One West Huanghe Road, Huai’an 223300, China (qlwang@njmu.edu.cn); Hongbing Shen, MD, PhD, Department of Epidemiology and Biostatistics, Jiangsu Key Lab of Cancer Biomarkers, Prevention, and Treatment, Collaborative Innovation Center for Cancer Medicine, School of Public Health, Nanjing Medical University, 101 Longmian Ave, Nanjing 211166, China (hbshen@njmu.edu.cn).

Author Contributions: Drs Luo and Zhang had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. Drs Luo, L. Yao, and Zhang contributed equally as co–first authors. Drs Wang and Shen contributed equally as senior authors.

Concept and design: L. Yao, Wang.

Acquisition, analysis, or interpretation of data: Luo, Zhang, M. Yao, Chen, L. Yao, Shen.

Drafting of the manuscript: Luo, M. Yao, Wang.

Critical revision of the manuscript for important intellectual content: Zhang, Chen, L. Yao, Wang, Shen.

Statistical analysis: Luo, Zhang, M. Yao, Chen.

Obtained funding: Luo, Wang.

Administrative, technical, or material support: Luo, L. Yao.

Supervision: Shen.

Conflict of Interest Disclosures: None reported.

Funding/Support: This study was supported by the National Natural Science Foundation of China, with award 81772585 to Dr Wang, award 81972739 to Dr Luo, and award 81800149 to Dr Zhang and the Key Laboratory Projects of Huai’an, with award HAP201804 to Dr Wang and award HAP201910 to Dr Zhang.

Role of the Funder/Sponsor: The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.