Observation and analysis of 26 cases of asymptomatic SARS-COV2 infection
Authors: Juan Zhou, Yingzheng Tan, Dan Li, Xiaojin He, Ting Yuan, Yunzhu Long
Journal: Journal of Infection (2020)

We read with interest the article in this journal which revealed that CT scanning provides important bases for early diagnosis and treatment of COVID-19 (Corona Virus Infection Disease 2019) which is caused by SARS-COV2 (Severe Acute Respiratory Syndrome Coronavirus 2).1Yu-Huan Xu Jing-Hui Dong Wei-Min An Xiao-Yan Lv Xiao-Ping Yin Jian-Zeng Zhang et al.Clinical and computed tomographic imaging features of novel coronavirus pneumonia caused by SARS-CoV-2.Journal of Infection. 2020; 0https://doi.org/10.1016/j.jinf.2020.02.017Abstract Full Text Full Text PDF Scopus (378) Google Scholar As a new infectious disease, the early identification of the source of the infection and the determination of the isolation time are the primary issues.2Van Beneden Chris A. Harald Pietz Kirkcaldy Robert D. Koonin Lisa M. Uyeki Timothy M. Oster Alexandra M. et al.Early Identification and Prevention of the Spread of Ebola - United States.MMWR Supplements. 2016; 65: 75-84https://doi.org/10.15585/mmwr.su6503a11Crossref PubMed Scopus (17) Google Scholar Recent studies have found that the emergence of asymptomatic SARS-COV2 infections.3Ruiyun Li Sen Pei Bin Chen Yimeng Song Tao Zhang Wan Yang et al.Substantial undocumented infection facilitates the rapid dissemination of novel coronavirus (COVID-19).MedRxiv. 2020; (2020.02.14.20023127)https://doi.org/10.1101/2020.02.14.20023127Crossref Scopus (0) Google Scholar Unexpectedly, the asymptomatic proportion was nearly about 18% in light of a statistical modeling analysis on the Diamond Princess cruise where an outbreak of SARS-COV2 infections occurred.4Kenji Mizumoto Katsushi Kagaya Alexander Zarebski Gerardo Chowell Estimating the Asymptomatic Proportion of 2019 Novel Coronavirus onboard the Princess Cruises Ship, 2020.MedRxiv. 2020; (2020.02.20.20025866)https://doi.org/10.1101/2020.02.20.20025866Crossref Scopus (0) Google Scholar Therefore, it is necessary to further clarify the infectivity and outcome of these asymptomatic infections. We observed and analyzed the phenotypic characteristics of asymptomatic individuals originating from the active detection of high-risk individuals who had close contacts with COVID-19 patients during isolated observation with viral nucleic acid positive. The epidemiological history, laboratory, radiologic data and outcomes were collected according to the medical records. A total of 26 cases of asymptomatic infection were detected as SARS-COV2 positive through swab specimen between January 20 to February 30. Among these, there were 10 males (38.5%), which was in line with another similar report,5Zhiliang Hu Ci Song Chuanjun Xu Guangfu Jin Yaling Chen Xin Xu et al.Clinical Characteristics of 24 Asymptomatic Infections with COVID-19 Screened among Close Contacts in Nanjing, China.MedRxiv. 2020; (2020.02.20.20025619)https://doi.org/10.1101/2020.02.20.20025619Crossref Scopus (0) Google Scholar and the average age was 37 years old, with the youngest being 3 years old and the oldest beings 90 years old. Five cases were under 18 (19.2%) and 4 cases were over 60 (15.4%). These data showed that people of different ages are generally susceptible to SARS-COV2, but the average age of asymptomatic patients is lower than the reported age of COVID-19 patients which was 40-70 years old (propinquity 73%).6Epidemiology Working Group for NCIP Epidemic Response. The epidemiological characteristics of an outbreak of 2019 novel coronavirus diseases (COVID-19) in China. Available athttp://html.rhhz.net/zhlxbx/004.htm. Accessed February 26, 2020, 2020.Google Scholar Except for one case from Wuhan, the others were local infection cases. It was found that the period between exposure to the source of infection to the discovery of nucleic acid positive was 5-22 days, with an average of 8 days. They had no obvious discomfort or clinical manifestations related to COVID-19 when were found to be positive for SARS-COV2. During the process of the quarantine, body temperature was daily monitored, and chest computed tomography (CT) regularly checked. Peripheral blood test results showed that the total number of white blood cells and lymphocytes in these patients were basically normal. The screening for pneumonia by chest CT found five cases with small area of glass exudative lesions on the edge of lung (Fig. 1A-C), implying that these individuals would be difficult to detect except through pathogen tests and chest CT scanning. Finally, 9 patients subsequently had respiratory infections symptoms such as cough and fever, lately they were diagnosed as COVID-19. In order to observe the outcome of the virus carriers, these asymptomatic infected persons were managed in isolation wards, and took Lopinavir-Ritonavir as well as Chinese medicine under the guidance of physicians to avoid possible progression to COVID-19. Eventually, these asymptomatic patients were discharged from hospital after two consecutive negative of viral nucleic acid test. Most importantly, a 37-year-old woman was confirmed to be significantly contagious. Her father was diagnosed as a COVID-19 patient on February 12 after her return home on January 22 from Wuhan; thereafter, an isolated observation was conducted. During this period, the virus was not detected to be positive until the fifth nucleic acid sampling test on February 15th which suggested an incubation period up to 22 days, and then turned negative on March 2. Meanwhile, no clinical symptoms and pulmonary imaging changes were found throughout the process. In addition, other cases who had close contact with a confirmed patient from Wuhan also caught our attention, and members of her family were in isolation after she was found to be an asymptomatic carrier. Subsequently, her father-in-law and mother-in-law were both detected as SARS-COV2 positive. These cases proved that asymptomatic SARS-COV2 carriers can also spread the virus before the nucleic acid test was positive, fully illustrating the importance of home isolation during the epidemic. The outbreak of the new coronavirus infection in 2019 was unexpected and poses a great threat to international public health security.6Epidemiology Working Group for NCIP Epidemic Response. The epidemiological characteristics of an outbreak of 2019 novel coronavirus diseases (COVID-19) in China. Available athttp://html.rhhz.net/zhlxbx/004.htm. Accessed February 26, 2020, 2020.Google Scholar Note that the SARS-COV2 spreads extremely quickly, and it probably resulted from the unrecognized asymptomatic carriers in the population which accounted for approximately 18% of total.4Kenji Mizumoto Katsushi Kagaya Alexander Zarebski Gerardo Chowell Estimating the Asymptomatic Proportion of 2019 Novel Coronavirus onboard the Princess Cruises Ship, 2020.MedRxiv. 2020; (2020.02.20.20025866)https://doi.org/10.1101/2020.02.20.20025866Crossref Scopus (0) Google Scholar,5Zhiliang Hu Ci Song Chuanjun Xu Guangfu Jin Yaling Chen Xin Xu et al.Clinical Characteristics of 24 Asymptomatic Infections with COVID-19 Screened among Close Contacts in Nanjing, China.MedRxiv. 2020; (2020.02.20.20025619)https://doi.org/10.1101/2020.02.20.20025619Crossref Scopus (0) Google Scholar Early detection and isolation of asymptomatic virus carriers is necessary in the current situation of epidemic control. None.