Since December 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection emerged in Wuhan, China, and rapidly spread throughout the world. 1, 2 As of 13 March 2020, a total of 132 536 confirmed patients with coronavirus disease 2019 (COVID-19) have been reported in 123 countries with 4947 deaths. 3 The epidemiologic, clinical, and radiologic characteristics of COVID-19 have been described by several studies. 1, 4, 5 Guan et al, 5 analyzed the clinical characteristics of 1099 patients with laboratory-confirmed COVID-19 and found that the COVID-19 has a wide spectrum of severity. The clinical spectrum of COVID-19 ranges from mild to critically ill cases with fatal outcomes. 5 Previous studies have only described the general epidemiological and clinical findings of patients of COVID-19. Recently, several studies have reported asymptomatic cases of SARS-CoV-2 infection. [6] [7] [8] [9] However, these asymptomatic cases were followed for a very short period.
Specific information that characterizes asymptomatic patients remains unknown. As reported by the previous study, fever as one of the dominant symptoms of COVID-19 was identified in only 43.8% of the patients on presentation, while 88.7% of patients developed a fever after hospitalization indicating that some asymptomatic COVID-19 cases before admission may develop symptoms during the hospitalization. 5 However, few studies have reported SARS-CoV-2 infected patients with completely asymptomatic throughout the disease course.
In this study, we investigated the epidemiological and clinical features of patients infected by SARS-CoV-2 with completely asymptomatic throughout the disease course.
Patients with confirmed SARS-CoV-2 infection were retrospectively recruited from 10 designated hospitals in 10 cities of Jiangsu province, China (Xuzhou, Lianyungang, Suqian, Huai'an, Yancheng, Nantong, Taizhou, Yangzhou, Changzhou, and Suzhou) from 18 January 2020 to 26 February 2020. All confirmed patients were diagnosed according to the criterion of the World Health Organization (WHO) interim guidance. 10 Patients with completely asymptomatic throughout the disease course were included for the final analysis.
The study was approved by the institutional ethics board of hospitals, with a waiver of informed consent.
The medical records of confirmed cases were reviewed by at least two healthcare staff in each hospital. The demographic characteristics, comorbidities, exposure history, symptoms, laboratory test results, radiological data, treatment, and outcomes were collected. The data were cross-checked by researchers to avoid errors. Unclear information of patients especially for the symptoms of the patients was further clarified through contacting the specific clinicians directly who were responsible for the treatment of patients. The criteria for discharge of patients was according to the guidelines for the diagnosis and treatment of novel coronavirus infection by the Chinese National Health Commission (Trial Version 5). 11 All patients were confirmed by throat swab samples or anal swab samples detecting by a real-time reverse transcriptasepolymerase chain reaction (RT-PCR) according to the protocol by the WHO. 12 Elevated serum CRP (≥10 mg/L) was observed in 6 (40.0%) patients (Table 3) . Table 4 ). 