key: cord-0808103-7w1bhaz6 authors: Tao, Y.; Cheng, P.; Chen, W.; Wan, P.; Chen, Y.; Yuan, G.; Chen, J.; Huo, D.; Guan, G.; Sun, D.; Tan, J.; Yang, G.; Zeng, W.; Zhu, C. title: High incidence of asymptomatic SARS-CoV-2 infection, Chongqing, China date: 2020-03-23 journal: nan DOI: 10.1101/2020.03.16.20037259 sha: 3fe2ed04f26d0c9b6928cdaa58113672a28a1741 doc_id: 808103 cord_uid: 7w1bhaz6 Background: SARS-CoV-2 has been a global pandemic, but the emergence of asymptomatic patients has caused difficulties in the prevention of the epidemic. Therefore, it is significant to understand the epidemiological characteristics of asymptomatic patients with SARS-CoV-2 infection. Methods: In this single-center, retrospective and observational study, we collected data from 167 patients with SARS-CoV-2 infection treated in Chongqing Public Health Medical Center (Chongqing, China) from January to March 2020. The epidemiological characteristics and variable of these patients were collected and analyzed. Findings: 82.04% of the SARS-CoV-2 infected patients had a travel history in Wuhan or a history of contact with returnees from Wuhan, showing typical characteristics of imported cases, and the proportion of severe Covid-19 patients was 13.2%, of which 59% were imported from Wuhan. For the patients who was returnees from Wuhan, 18.1% was asymptomatic patients. In different infection periods, compared with the proportion after 1/31/2020, the proportion of asymptomatic patient among SARS-CoV-2 infected patient was higher(19% VS 1.5%). In different age groups, the proportion of asymptomatic patient was the highest(28.6%) in children group under 14, next in elder group over 70 (27.3%). Compared with mild and common Covid-19 patients, the mean latency of asymptomatic was longer (11.25 days VS 8.86 days), but the hospital length of stay was shorter (14.3 days VS 16.96 days) . Conclusion: The SARS-CoV-2 prevention needs to focus on the screening of asymptomatic patients in the community with a history of contact with the imported population, especially for children and the elderly population. WHO has announced on March 11 in Switzerland that SARS-CoV-2 has the characteristics of a global pandemic 1 . As of March 15, 2020, China has accumulated 81,048 cases of SARS-CoV-2 infection and a mortality rate of 3.95 %, also, there is a total of 64322 cases expect China, with a mortality rate of 3.51% 1,2 . The proportion of asymptomatic patients has gradually increased 3 . Asymptomatic patients are still highly contagious, paying special attention to the epidemiological characteristics of asymptomatic patients is of great significance for the control of the epidemic. The clinical data of 167 SARS-CoV-2 infected patients treated in Chongqing Public Health Medical Center from January 2020 to March 2020 were collected. COVID-19 is diagnosed according to the WHO Interim Guidelines 6 . The severity of COVID -19 was defined according to the American Thoracic Society's Community Acquired Pneumonia Guidelines 7 . A confirmed case of SARS-CoV-2 infection was defined as a positive result on RT-PCR assay of nasal and pharyngeal swab specimens. This study was approved by the Ethics Committee of Chongqing Public Health Medical Treatment Center (NO.2020-018-01-KY), informed consent was allowed to be waived. We reviewed and analyzed the clinical files, radiologic and laboratory results of all 167 patients. All data are completed through independent survey forms to ensure that they do not interfere with each other. At the same time, three investigators complete the data collection and management to ensure the independence, completeness and authenticity of the data. The detection of SARS-CoV-2 was determined based on new coronavirus pneumonia diagnosis and treatment plan developed by the National Health Committee of the People's Republic of China. All the patients performed the RT-PCR assay of nasal and pharyngeal swab specimens for SARS-CoV-2 detection 8 . Radiologic and laboratory detection of all patients were completed according to normal inspection procedures. Statistical Analysis Data in the full text are expressed as median, mean ± SD, or percentage. The missing data are not counted. Statistical analysis in this study were conducted with SPSS 25.0. There were 22 patients with severe COVID-19, and the proportion of severe Table 2 for the detailed data. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not peer-reviewed) The copyright holder for this preprint Data are median (IQR), n (%) or mean (SD). Some patients lack certain tests, or some patients' mean latency is unknown. White blood cell count (× 10⁹ cells per L). Lymphocyte count (× 10⁹ cells per L) . Platelet count, × 10⁹ per L. ARDS=acute respiratory distress syndrome. Patients means people who have confirmed SARS-CoV-2 infection or are highly suspected of being infected. For the asymptomatic patients, compared with mild and common Covid-19 patients, the mean latency of 50-59 age group (7 days vs. 9.6 days) and children group (9 days vs. 11.7 days) were shorter, and other age group was significantly longer, especially in the 30-39 age group (20.5 days vs. 7.2 days), existence C-reactive protein (3 cases, 15% . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint . https://doi.org/10.1101/2020.03.16.20037259 doi: medRxiv preprint vs. 33 cases, 26.4%) and procalcitonin (2 cases, 10% vs. 11 cases, 8.8%) increase. Most of the asymptomatic patients did not show typical and abnormal clinical characteristics, radiologic and laboratory indexes, only 1 (5%) had myocardial injury. In particular, some of the asymptomatic patients also had atypical changes in the radiologic indexes, which were not the diagnostic criterion of Covid-19, such as bronchiectasis, general inflammatory changes in the lung, etc. For the asymptomatic patients over the age of 70, there were 2 (66.67%) patients with ground-glass opacity in radiologic examination. All the SARS-CoV-2 infected patients were treated according to the new coronavirus pneumonia diagnosis and treatment plan developed by the National Health Committee of the People's Republic of China. At present, all the patients have recovered. For the asymptomatic patients, compared with the mild and common Covid-19 patient, the hospital length of stay in children group was prolonged (16.5 days vs 9.8 days). See Table 3 and Table S1 for the detailed data. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint increase the mean latency due to its cryptic nature. However, the hospital length of stay may be shorten due to decreased toxicity during transmission. In addition, the mean latency was long in children and older group(10.8 days, 11.3 days). Overall, the hospital length of stay increases with age. This suggests that in the process of epidemic prevention and control, special attention needs to be paid to children and elderly people. See Table 4 for the detailed data. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint . https://doi.org/10.1101/2020.03.16.20037259 doi: medRxiv preprint A 34-year-old woman was admitted at 1.31(nonsevere), without comoebidities, had been to Wuhan 5 days ago. The CT scan revealed scattered infections in both lungs. White-cell count is 2.69× 10⁹ cells per L, Neutrophil ratio is 54.3%, Lymphocyte count is 0.96× 10⁹ cells per L , not admitted to the ICU. Nineteen days later, she was discharged healthy. Upon discharge, the CT scan of her discharge revealed improvement in the absorption of both lung lesions, White-cell count is 5.43× 10⁹ cells per L, Lymphocyte count is 1.21× 10⁹ cells per L . A 44-year-old man was admitted at 2.04(nonsevere), without comoebidities, had not contacted Wuhan returnees or traveled to Wuhan. The CT scan revealed scattered infections in both lungs. White-cell count is 2.36× 10⁹ cells per L, Neutrophil ratio is 60.6%, Lymphocyte count is 0.6× 10⁹ cells per L, CD4 + T cell count is 196, CD8 + T cell count is 89, CD4 + /CD8 + is 2.22, C-reactive protein is 26.23 mg/L, Procalcitonin is normal, not admitted to the ICU. Eighteen days later, he was discharged healthy. Upon discharge, the CT scan revealed improvement in the absorption of both lung lesions, White-cell count is 5.43× 10⁹ cells per L, Lymphocyte count is 1.16× 10⁹ cells per L . A 38-year-old man was admitted at 1.29(severe), without comoebidities, had contact with returnees from Wuhan 4 days ago. The CT scan revealed potential small patchy, flaky ground glass shadows on both lungs. White-cell count is 5.89× 10⁹ cells per L, Neutrophil ratio is 75.6%, Lymphocyte count is 2.58× 10⁹ cells per L, CD4 + T cell count is 252/ul, CD8 + T cell count is 305/ul, CD4 + /CD8 + is 0.83, C-reactive protein is 71.45 mg/L, Procalcitonin is 0.073 ng/ml, not admitted to the ICU. Twentynine days later, he was discharged healthy. Upon discharge, the CT scan revealed the lungs were scattered in stellate, patchy, grid-like ground glass stoves, and cord shadows. White-cell count is 5.77× 10⁹ cells per L, Lymphocyte count is 1.55× 10⁹ cells per L, CD4 + T cell count is 299/ul, CD8 + T cell count is 264/ul, CD4 + /CD8 + is 0.83. As the epidemic develops, the proportion of asymptomatic patients is getting higher and higher (up to 19% in the onset after February 1 st , 2020). The mean latency of asymptomatic patients with SARS-CoV-2 infection was prolonged (10.5 days), but the hospital length of stay was shortened (14.3 days). All countries have adopted isolation measures for imported populations from areas or countries with severe SARS-CoV-2 infection, and treated patients with symptoms who have a history of contact with this imported population 1 . However, a large number of asymptomatic patients with contact history with imported cases failed to be included in the focus surveillance. Our study shows for the first time that asymptomatic patients with SARS-CoV-2 infection have a contact history with imported case account for a large proportion. Therefore, the next stage of SARS-CoV-2 prevention and control needs to focus on the screening of asymptomatic patients in the community with a history of contact with the imported population, especially for children and the elderly. We declare no competing interests. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint . https://doi.org/10.1101/2020.03.16.20037259 doi: medRxiv preprint After publication, the data will be made available to others on reasonable requests to the corresponding author. A proposal with detailed description of study objectives and statistical analysis plan will be needed for evaluation of the reasonability of requests. Additional materials might also be required during the process of evaluation. Deidentified participant data will be provided after approval from the corresponding author and Chongqing Public Health Medical Center . . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not peer-reviewed) The copyright holder for this preprint Data are median (IQR), n (%) or mean (SD). Some patients lack certain tests, or some patients' mean latency is unknown. White blood cell count (× 10⁹ cells per L). Lymphocyte count (× 10⁹ cells per L) . Platelet count, × 10⁹ per L. ARDS=acute respiratory distress syndrome. Patients means people who have confirmed SARS-CoV-2 infection or are highly suspected of being infected. World Health Organization. Coronavirus disease (COVID-19) outbreak National Health Commission of the People's Republic of China home page Serial interval of COVID-19 from publicly reported confirmed cases Emerg Infect Dis Home Page of Wuhan Municipal Health Commission Home Page of Chongqing Health Committee Clinical management of severe acute respiratory infection when novel coronavirus (2019-nCoV) infection is suspected: interim guidance We thank all patients and their families involved in the study. We thank all doctors