key: cord-0779803-bmsmegbs authors: Song, Huan; Xiao, Jun; Qiu, Jiajun; Yin, Jin; Yang, Huazhen; Shi, Rui; Zhang, Wei title: A considerable proportion of individuals with asymptomatic SARS-CoV-2 infection in Tibetan population date: 2020-03-30 journal: nan DOI: 10.1101/2020.03.27.20043836 sha: bd8b87c762b20328de264fbfcaec9e703f94ae89 doc_id: 779803 cord_uid: bmsmegbs Severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2) quickly became a major epidemic threat in the whole China. We analysed SARS-Cov-2 infected cases from Tibetan Autonomous Prefecture, and noted divergent characteristics of these Tibetans infected cases compared to Han Chinese, characterizing by a considerable proportion of asymptomatic carriers (21.7%), and few symptomatic patients with initial symptom of fever (7.7%). Here, we did a descriptive study on clinical characteristics of 18 asymptomatic individuals with SARS-CoV-2 infection. The median age of these asymptomatic carriers was 31 years and one third of them were students, aged under 20 years. Notably, some of asymptomatic carriers had recognizable changes in radiological and laboratory indexes. Our finding indicates a potentially big number of SARS-CoV-2 asymptomatic carriers in prevalent area, highlighting a necessity of screening individuals with close contact of infected patients, for a better control on the spread of SARS-CoV-2 infection. . CC-BY-ND 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted March 30, 2020. . https://doi.org/10.1101/2020. 03.27.20043836 doi: medRxiv preprint Severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2) quickly became a major epidemic threat in the whole China. We analysed SARS-Cov-2 infected cases from Tibetan Autonomous Prefecture, and noted divergent characteristics of these Tibetans infected cases compared to Han Chinese, characterizing by a considerable proportion of asymptomatic carriers (21.7%), and few symptomatic patients with initial symptom of fever (7.7%). Here, we did a descriptive study on clinical characteristics of 18 asymptomatic individuals with SARS-CoV-2 infection. The median age of these asymptomatic carriers was 31 years and one third of them were students, aged under 20 years. Notably, some of asymptomatic carriers had recognizable changes in radiological and laboratory indexes. Our is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted March 30, 2020. . https://doi.org/10.1101/2020.03.27.20043836 doi: medRxiv preprint research, we did a descriptive study on clinical characteristics of 18 asymptomatic individuals with SARS-CoV-2 infection. We conducted a retrospective, single-centre study based on the People's Hospital of Daofu county. More than 90% of locally confirmed infected cases were recruited between 26th Jan and 28th February 2020. We defined asymptotic infected cases as the ones who got positive results on PCR test for SARS-Cov-2 infection but without any clinical symptoms during the whole surveillance period. Information on epidemiological, demographic characteristics, clinical features, treatment, and outcome were extracted from patients' medical records. Clinical data were followed up until 6th March, 2020. The study was approved by West China Hospital Ethics Committee (reference no.2020-190) and written informed consent was obtained from patients in People's Hospital of Daofu county before enrolment. 18 (18/83, 21.7%) individuals were identified as asymptomatic carriers, with a predominant distribution of males (61.0%) ( Table 1 ). The median age was 31 years and one third of the asymptomatic individuals were students, aged under 20 years. Only 1 infected people (5.6%) had pre-existed chronic illness. Epidemiological data showed all the infection were caused by community transmission. Notably, some of asymptomatic carriers had recognizable changes in radiological and laboratory indexes. 7(38.9%) cases had abnormalities in chest computed tomography (CT), representing as unilateral or bilateral patchy shadowing or/and ground-glass opacity (Table 1) . 9(50.0%), 7(38.8%), and 15(83.3%) cases obtained abnormal results in tests of blood routine, is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted March 30, 2020. . https://doi.org/10.1101/2020.03.27.20043836 doi: medRxiv preprint coagulation function, and blood biochemistry, respectively (details shown in Table 2 ). All asymptomatic carriers received antiviral treatment and were charged at the time of data analysis. The average duration of hospital stay was 13 days. To our knowledge, this is the first descriptive study specifically focusing on a group of asymptomatic individuals with SARS-CoV-2 infection. We found that in Tibetan population, asymptomatic carriers were mainly young or middle-aged healthy individuals, with their infections disappeared after antiviral treatment. Importantly, although no clinical symptoms, many of them have typically viral pneumonia-like changes in chest CT images and abnormal laboratory measures. The possible abnormal findings on chest CT images among asymptomatic carriers got support from one previous report [2] . However, the common abnormalities in blood tests was never described before [2] [3] [4] . Also, it is notable that there is a considerable proportion of asymptomatic carriers among our study population (21.7%), which was much higher than the rate reported previously (5%) [5] . This may due to a high screening rate for individuals with exposure history in Ganzi area. Alternatively, the genetic variations between Han Chinese and Tibetans may be attributable for these differences. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint Agricultural worker 11(61.11) Oxygen therapy 9 (50.00) Self-employed 0 (0) Mechanical ventilation 0 (0) is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint Procalcitonin (ng/mL; normal range <0.5) <0.5 C-reactive protein (mg/L; normal range 0-10) 5.03(0.12) * Changes (i.e., above or below the normal rang) were summarized as number of increase/decrease (% of involved individuals.) . CC-BY-ND 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted March 30, 2020. . https://doi.org/10.1101/2020.03.27.20043836 doi: medRxiv preprint Outbreak of pneumonia of unknown etiology in Wuhan, China: The mystery and the miracle A familial cluster of pneumonia associated with the 2019 novel coronavirus indicating person-to-person transmission: a study of a family cluster Presumed Asymptomatic Carrier Transmission of COVID-19 Asymptomatic cases in a family cluster with SARS-CoV-2 infection. The Lancet Infectious diseases Characteristics of COVID-19 infection in Beijing. The Journal of infection We thank Yao Hu, Junren Wang, Jingwei Jiang, Tingxi Zhu, Yilong Chen, Xiaoxi Zeng, Chunyang Li, Yajing Sun, Yonghong Gu, Chao Zhang, for data extraction and data cleaning. None of these individuals received compensation for their contributions. No potential conflict of interest was reported by the author(s).