1.Surgical efficacy and prognosis influencing factors of hilar cholangiocarcinoma based on multi-disciplinary diagnosis and treatment
Liang MAO ; Yifei YANG ; Alexer ABAYDULLA ; Tie ZHOU ; Xu FU ; Hao CHENG ; Jing ZHANG ; Youjun LIANG ; Yinyin FAN ; Wentao KONG ; Jian HE ; Aimei LI ; Min TANG ; Qun ZHOU ; Qibin HE ; Yi WANG ; Lei WANG ; Weiwei KONG ; Jie SHEN ; Baorui LIU ; Jun CHEN ; Jiong SHI ; Qi LI ; Zhao LIU ; Yudong QIU
Chinese Journal of Digestive Surgery 2023;22(7):873-883
Objective:To investigate the surgical efficacy and prognosis influencing factors of hilar cholangiocarcinoma based on multidisciplinary diagnosis and treatment.Methods:The retrospective cohort study was conducted. The clinicopathological data of 91 patients with hilar cholangiocarcinoma who underwent surgery in Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School from April 2004 to April 2021 were collected. There were 59 males and 32 females, aged (61±10)years. Patients who were admitted from April 2004 to March 2014 underwent traditional surgical diagnosis and treatment, and patients who were admitted from April 2014 to April 2021 underwent multidisciplinary diagnosis and treatment. Observation indica-tors: (1) surgical situations; (2) postoperative situations; (3) postoperative pathological examina-tions; (4) postoperative prognosis analysis; (5) influencing factors of postoperative prognosis. Follow-up was conducted using telephone interview and outpatient examination. Patients were followed up once every 6 months after surgery to detect survival. The follow-up was up to April 2023. Measure-ment data with normal distribution were represented as Mean± SD, and comparison between groups was conducted using the independent sample t test. Measurement data with skewed distribution were represented as M(range), and comparison between groups was conducted using the Mann-Whitney U test. Comparison of ordinal data was conducted using the rank sum test. Count data were described as absolute numbers or percentages, and comparison between groups was conducted using the chi-square test or Fisher exact probability. The Kaplan-Meier method was used to draw survival curve and calculate survival rate. The Log-Rank test was used for survival analysis. Univariate and multivariate analyses were conducted using the COX proportional hazard model. Results:(1) Surgical situations. Of the 91 patients, there were 65 cases receiving hemi- or expanded hemi-hepatectomy, 13 cases receiving tri-hepatectomy, 9 cases receiving partial hepatectomy, 4 cases receiving extrahepatic bile duct resection. There were 24 cases receiving combined vein resection and reconstruction, 8 cases receiving combined pancreaticoduodenectomy, 6 cases receiving com-bined hepatic artery resection and reconstruction, including 24 cases receiving extended radical surgery (tri-hepatectomy, hepatic artery resection and reconstruction, hepatopancreaticoduodenec-tomy). The operation time, volume of intraoperative blood loss and intraoperative blood transfusion rate of 91 patients was (590±124)minutes, 800(range, 500?1 200)mL and 75.8%(69/91), respectively. Of the 91 patients, cases receiving extended radical surgery, the volume of intraoperative blood loss were 4, 650(range, 300?1 000)mL in the 31 patients who were admitted from April 2004 to March 2014, versus 20, 875 (range, 500?1 375)mL in the 60 patients who were admitted from April 2014 to April 2021, showing significant differences between them ( χ2=4.39, Z=0.31, P<0.05). (2) Post-operative situations. The postoperative duration of hospital stay and cases with postoperative infectious complications were (27±17)days and 50 in the 91 patients. Cases with abdominal infection, cases with infection of incision, cases with bacteremia and cases with pulmonary infection were 43, 7, 5, 8 in the 91 patients. One patient might have multiple infectious complications. Cases with bile leakage, cases with delayed gastric emptying, cases with chylous leakage, cases with liver failure, cases with pancreatic fistula, cases with intraperitoneal hemorrhage, cases with reoperation, cases dead during the postoperative 90 days were 30, 9, 9, 6, 5, 3, 6, 3 in the 91 patients. Cases with abdominal infection was 10 in the 31 patients who were admitted from April 2004 to March 2014, versus 33 in the 60 patients who were admitted from April 2014 to April 2021, showing a significant difference between them ( χ2=4.24, P<0.05). Cases dead during the postoperative 90 days was 3 in the 31 patients who were admitted from April 2004 to March 2014, versus 0 in the 60 patients who were admitted from April 2014 to April 2021, showing a significant difference between them ( P<0.05). (3) Post-operative pathological examinations. Of the 91 patients, cases with Bismuth type as type Ⅰ?Ⅱ, type Ⅲ, type Ⅳ, cases with T staging as Tis stage, T1 stage, T2a?2b stage, T3 stage, T4 stage, cases with N staging as N0 stage, N1 stage, N2 stage, cases with M staging as M0 stage, M1 stage, cases with TNM staging as 0 stage, Ⅰ stage, Ⅱ stage, Ⅲ stage, ⅣA stage, ⅣB stage, cases with R 0 radical resection, cases with R 1 or R 2 resection were 15, 46, 30, 1, 9, 25, 30, 26, 49, 36, 6, 85, 6, 1, 7, 13, 58, 6, 6, 63, 28. Cases with R 0 radical resection, cases with R 1 or R 2 resection were 15, 16 in the 31 patients who were admitted from April 2004 to March 2014, versus 48, 12 in the 60 patients who were admitted from April 2014 to April 2021, showing a significant difference between them ( χ2=9.59, P<0.05). (4) Postoperative prognosis analysis. Of the 91 patients, 3 cases who died within 90 days after surgery were excluded, and the 5-year overall survival rate and median overall survival time of the rest of 88 cases were 44.7% and 55 months. The 5-year overall survival rate was 33.5% in the 28 patients who were admitted from April 2004 to March 2014, versus 50.4% in the 60 patients who were admitted from April 2014 to April 2021, showing a significant difference between them ( χ2=5.31, P<0.05). Results of further analysis showed that the corresponding 5-year overall survival rate of cases without lymph node metastasis was 43.8% in the 16 patients who were admitted from April 2004 to March 2014, versus 61.6% in the 31 patients who were admitted from April 2014 to April 2021. There was a significant difference in the 5-year overall survival rate between these patients without lymph node metastasis ( χ2=3.98, P<0.05). The corresponding 5-year overall survival rate of cases with lymph node metastasis was 18.5% in the 12 patients who were admitted from April 2004 to March 2014, versus 37.7% in the 29 patients who were admitted from April 2014 to April 2021. There was no significant difference in the 5-year overall survival rate between these patients with lymph node metastasis ( χ2=2.25, P>0.05). (5) Influencing factors of postoperative prognosis. Results of multivariate analysis showed that poorly differentiated tumor and R 1 or R 2 resection were inde-pendent risk factors influencing prognosis after surgical treatment of hilar cholangiocarcinoma ( hazard ratio=2.62, 2.71, 95% confidence interval as 1.30?5.29, 1.30?5.69, P<0.05). Conclusions:Compared with traditional surgical diagnosis and treatment, treatment of hilar cholangiocarcinoma based on multidisciplinary diagnosis and treatment can expand surgical indications, reduce proportion of dead patients within 90 days after surgery, improve proportation of radical resection and long-term survival rate. Poorly differentiated tumor and R 1 or R 2 resection are independent risk factors influencing prognosis after surgical treatment of hilar cholangiocarcinoma.
2.Correction to: Rescue of premature aging defects in Cockayne syndrome stem cells by CRISPR/Cas9-mediated gene correction.
Si WANG ; Zheying MIN ; Qianzhao JI ; Lingling GENG ; Yao SU ; Zunpeng LIU ; Huifang HU ; Lixia WANG ; Weiqi ZHANG ; Keiichiro SUZUIKI ; Yu HUANG ; Puyao ZHANG ; Tie-Shan TANG ; Jing QU ; Yang YU ; Guang-Hui LIU ; Jie QIAO
Protein & Cell 2022;13(8):623-625
3.Analysis on characteristics and influencing factors of COVID-19 confirmed cases with viral nucleic acid re-positive after discharge in Guangdong Province.
Xiao Hua TAN ; Min KANG ; Ai Ping DENG ; Bai Sheng LI ; Min LUO ; Yao YI ; YaLi ZHUANG ; YingTao ZHANG ; Tie SONG
Chinese Journal of Preventive Medicine 2022;56(1):49-55
Objective: To analyze the epidemiological characteristics and influencing factors of COVID-19 confirmed cases with viral nucleic acid re-positive in anal and/or throat swabs after discharge during the domestic imported epidemic stage in Guangdong Province in early 2020. Methods: The COVID-19 confirmed cases with the onset time before March 1, 2020 in Guangdong Province were collected to analyze the demographic data, epidemiological characteristics, and specimen collection and testing data after discharge. Logistic regression model was used for influencing factors analysis of re-positive cases. Results: A total of 1 286 COVID-19 confirmed cases were included, the M(Q1,Q3) of age was 44(32,58)years, 617 cases were male, 224 cases were re-positive in anal and/or throat swabs with the re-positive rate 17.42%. The M(Q1,Q3) of age of re-positive cases was 35(23, 50) years, which was younger than that of re-negative cases age was those 46(33, 59) years (P<0.001). With the increase of age, re-positive rate decreased (χ2trend=52.73, P<0.001). 85.27% (191/224) of re-positive cases were found in 14 d after discharge, the duration time of re-positive status was 13(7, 24) d, and 81.69% (183/224) of re-positive cases were re-tested negative in 28 d after re-positive date. No fever and other symptoms had been observed among re-positive cases during the whole follow-up. No secondary infectious cases had been found among close contacts after 14 d of centralized isolation and sampling screening. Univariate logistic regression model analysis revealed that the influencing factors of the re-positive cases included age, occupation, clusters, clinical types, and admission time. Multivariate logistic regression model analysis revealed that age was an independent risk factor. Conclusions: SARS-CoV-2 viral nucleic acid re-positive is found in COVID-19 confirmed cases after discharge in Guangdong Province. Most re-positive cases are confirmed among 14 d after discharge and re-test to negative among 28 d after re-positive date. Age is an risk factor for re-positive cases after discharge.
COVID-19
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China/epidemiology*
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Epidemics
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Humans
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Male
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Nucleic Acids
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SARS-CoV-2
4.Effects of Exogenous Substances on Growth of Polyporus umbellatus Mycelium and Its Polysaccharide Content
Yuan ZHENG ; Yang-hua LI ; Peng-jie HAN ; Yu-yang ZHAO ; Jun-hui ZHOU ; Tie-gui NAN ; Quan YANG ; Min ZHANG ; Yuan YUAN
Chinese Journal of Experimental Traditional Medical Formulae 2021;27(14):129-137
Objective:To explore the effects of diverse exogenous substances at different concentrations on the growth of
6. Clinical outcomes of COVID-19 cases and influencing factors in Guangdong province
Yingtao ZHANG ; Aiping DENG ; Ting HU ; Xuguang CHEN ; Yali ZHUANG ; Xiaohua TAN ; Huizheng ZHEN ; Limei SUN ; Yan LI ; Haojie ZHONG ; Jianfeng HE ; Tie SONG ; Min KANG
Chinese Journal of Epidemiology 2020;41(0):E057-E057
Objective To analyze the clinical courses and outcomes of COVID-19 cases and the influencing factors in Guangdong province and provide basis for the formulation or adjustment of medical care and epidemic control strategy for COVID-19. Methods We collected demographic data, medical histories, clinical courses and outcomes of 1 350 COVID-19 patients reported in Guangdong as of 4 March 2020 via epidemiological investigation and process tracking. Disease severity and clinical course characteristics of the patients and influencing factors of severe illness were analyzed in our study. Results Among 1 350 cases of COVID-19 cases in Guangdong, 72 (5.3%) and 1049 (77.7%) were mild and ordinary cases, 164 (12.1%) were severe cases, 58 (4.3%) were critical cases and 7 (0.5%) were fatal. The median duration of illness were 23 days ( P 25 - P 75 : 18-31 days) and the median length of hospitalization were 20 days ( P 25 - P 75 : 15-27 days). For severe cases, the median time of showing severe manifestations was on the 12th day after onset ( P 25 - P 75 : 9th to 15th days), and the median time of severe manifestation lasted for 8 days P 25 - P 75 : 4-14 days). Among 1 066 discharged/fetal cases, 36.4% (36/99) and 1.0% (1/99) of the mild cases developed to ordinary cases and severe cases respectively after admission; and 5.2% (50/968) and 0.6% (6/968) of the ordinary cases developed to severe cases, and critical cases respectively after admission. In severe cases, 11.4% developed to critical cases (10/88). The influencing factors for severe illness or worse included male (a HR =1.87, 95% CI : 1.43-2.46), older age (a HR =1.67, 95% CI : 1.51-1.85), seeking medical care on day 2-3 after onset (a HR =1.73, 95% CI : 1.20-2.50) pre-existing diabetes (a HR =1.75, 95% CI : 1.12-2.73) and hypertension (a HR =1.49, 95% CI : 1.06-2.09). Conclusions The course of illness and length of hospitalization of COVID-19 cases were generally long and associated with severity of disease clinical outcomes. The severe cases were mainly occurred in populations at high risk. In the epidemic period, classified management of COVID-19 cases should be promoted according to needs for control and prevention of isolation and treatment for the purpose of rational allocation of medical resources.
7.A drug-eluting Balloon for the trEatment of coronarY bifurcatiON lesions in the side branch: a prospective multicenter ranDomized (BEYOND) clinical trial in China.
Quan-Min JING ; Xin ZHAO ; Ya-Ling HAN ; Ling-Ling GAO ; Yang ZHENG ; Zhan-Quan LI ; Ping YANG ; Hong-Liang CONG ; Chuan-Yu GAO ; Tie-Min JIANG ; Hui LI ; Jun-Xia LI ; Dong-Mei WANG ; Geng WANG ; Zhan-Chun CONG ; Zhong ZHANG
Chinese Medical Journal 2020;133(8):899-908
BACKGROUND:
Treatment of coronary bifurcation lesions remains challenging; a simple strategy has been preferred as of late, but the disadvantage is ostium stenosis or even occlusion of the side branch (SB). Only a few single-center studies investigating the combination of a drug-eluting stent in the main branch followed by a drug-eluting balloon in the SB have been reported. This prospective, multicenter, randomized study aimed to investigate the safety and efficacy of a paclitaxel-eluting balloon (PEB) compared with regular balloon angioplasty (BA) in the treatment of non-left main coronary artery bifurcation lesions.
METHODS:
Between December 2014 and November 2015, a total of 222 consecutive patients with bifurcation lesions were enrolled in this study at ten Chinese centers. Patients were randomly allocated at a 1:1 ratio to a PEB group (n = 113) and a BA group (n = 109). The primary efficacy endpoint was angiographic target lesion stenosis at 9 months. Secondary efficacy and safety endpoints included target lesion revascularization, target vessel revascularization, target lesion failure, major adverse cardiac and cerebral events (MACCEs), all-cause death, cardiac death, non-fatal myocardial infarction, and thrombosis in target lesions. The main analyses performed in this clinical trial included case shedding analysis, base-value equilibrium analysis, effectiveness analysis, and safety analysis. SAS version 9.4 was used for the statistical analyses.
RESULTS:
At the 9-month angiographic follow-up, the difference in the primary efficacy endpoint of target lesion stenosis between the PEB (28.7% ± 18.7%) and BA groups (40.0% ± 19.0%) was -11.3% (95% confidence interval: -16.3% to -6.3%, Psuperiority <0.0001) in the intention-to-treat analysis, and similar results were recorded in the per-protocol analysis, demonstrating the superiority of PEB to BA. Late lumen loss was significantly lower in the PEB group than in the BA group (-0.06 ± 0.32 vs. 0.18 ± 0.34 mm, P < 0.0001). For intention-to-treat, there were no significant differences between PEB and BA in the 9-month percentages of MACCEs (0.9% vs. 3.7%, P = 0.16) or non-fatal myocardial infarctions (0 vs. 0.9%, P = 0.49). There were no clinical events of target lesion revascularization, target vessel revascularization, target lesion failure, all-cause death, cardiac death or target lesion thrombosis in either group.
CONCLUSIONS:
In de novo non-left main coronary artery bifurcations treated with provisional T stenting, SB dilation with the PEB group demonstrated better angiographic results than treatment with regular BA at the 9-month follow-up in terms of reduced target lesion stenosis.
TRIAL REGISTRATION
ClinicalTrials.gov, NCT02325817; https://clinicaltrials.gov.
8.A multicenter survey of antibiotic use in very and extremely low birth weight infants in Hunan Province.
Ming-Jie WANG ; Shao-Jie YUE ; Jin LIN ; Xi-Rong GAO ; Xiao-Ming PENG ; Meng-Yu CHEN ; Hua-Bao PENG ; Bei CAO ; Yun-Qing ZENG ; Shu-Lian WANG ; Bo WEN ; Xi-Lin HUANG ; Xiao-Ping LI ; Ai-Zhen ZHANG ; Ting CAO ; Yi-Hua CHEN ; Tie-Qiang CHEN ; Chun-Hua YE ; Tao BO ; De-Lin JIANG ; Xiu-Qun HUANG ; Na-Fang REN ; Long-Zhang TAO ; Fang YAO ; Chang-Jun TIAN ; Hong-Ming LI ; Ai-Min ZHANG ; Fu-Rong HUANG ; Wei-Guo ZHANG ; Xiang-Hong CHEN ; Yu-Chan LIU ; Zheng-Lin LIU ; Yan-Shan XU ; Jing-Song MING ; Li CHEN ; Ning-Yi ZHU ; Jun-Min HE ; Sai-Jun YI ; Tuan-Mei WANG ; Zhao-Hui LI ; Gui-Tian WANG
Chinese Journal of Contemporary Pediatrics 2020;22(6):561-566
OBJECTIVE:
To investigate the current status of antibiotic use for very and extremely low birth weight (VLBW/ELBW) infants in neonatal intensive care units (NICUs) of Hunan Province.
METHODS:
The use of antibiotics was investigated in multiple level 3 NICUs of Hunan Province for VLBW and ELBW infants born between January, 2017 and December, 2017.
RESULTS:
The clinical data of 1 442 VLBW/ELBW infants were collected from 24 NICUs in 2017. The median antibiotic use duration was 17 days (range: 0-86 days), accounting for 53.0% of the total length of hospital stay. The highest duration of antibiotic use was up to 91.4% of the total length of hospital stay, with the lowest at 14.6%. In 16 out of 24 NICUs, the antibiotic use duration was accounted for more than 50.0% of the hospitalization days. There were 113 cases with positive bacterial culture grown in blood or cerebrospinal fluid, making the positive rate of overall bacterial culture as 7.84%. The positive rate of bacterial culture in different NICUs was significantly different from 0% to 14.9%. The common isolated bacterial pathogens Klebsiella pneumoniae was 29 cases (25.7%); Escherichia coli 12 cases (10.6%); Staphylococcus aureus 3 cases (2.7%). The most commonly used antibiotics were third-generation of cephalosporins, accounting for 41.00% of the total antibiotics, followed by penicillins, accounting for 32.10%, and followed by carbapenems, accounting for 13.15%. The proportion of antibiotic use time was negatively correlated with birth weight Z-score and the change in weight Z-score between birth and hospital discharge (r=-0.095, -0.151 respectively, P<0.01), positively correlated with death/withdrawal of care (r=0.196, P<0.01).
CONCLUSIONS
Antibiotics used for VLBW/ELBW infants in NICUs of Hunan Province are obviously prolonged in many NICUs. The proportion of routine use of third-generation of cephalosporins and carbapenems antibiotics is high among the NICUs.
Anti-Bacterial Agents
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Birth Weight
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Humans
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Infant
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Infant, Extremely Low Birth Weight
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Infant, Newborn
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Intensive Care Units, Neonatal
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Surveys and Questionnaires
9.Exhaustion of CD8 T cell immune functions in spleen of mice with different doses of Echinococcus multilocularis infections
Xin-Ling HOU ; Liang LI ; Ling-Hui LI ; Jing LI ; Hui WANG ; Tie-Min JIANG ; Rui-Qing ZHANG ; Ying-Mei SHAO ; Chuan-Shan ZHANG
Chinese Journal of Schistosomiasis Control 2020;32(6):591-597
ObjectiveTo examine the changes in the immune functions of CD8+ T cells in the spleen of mice following Echinococcus multilocularis infections at various doses and at different time points. MethodsThe E. multilocularis protoscoleces were collected, and E. multilocularis infection was modeled in mice via the hepatic portal vein at doses of 50 (low-dose), 500 (medium-dose) and 2 000 protoscoleces (high-dose), while physiological saline served as controls. Mouse spleen was isolated 2 (earlystage), 12 (middle-stage) and 24 weeks post-infection (late-stage), and spleen lymphocytes were harvested. The phenotype of memory CD8+ T cells and 2B4 expression were quantified in the mouse spleen, and the secretion of interferon (IFN)-γ, tumor necrosis factor (TNF)-α, interleukin (IL)-17A and IL-10 was measured. Results A central-memory phenotype was predominant in the CD8+ T cells in the spleen of mice at the early stage of high-dose protoscolece infections, and the proportion of central-memory CD8+ T cells was significantly greater in the high-dose group than in the control group (35.50% ± 2.00% vs. 25.90% ± 2.46%, P < 0.01), while a effector- memory phenotype was predominant in the CD8+ T cells in the spleen of mice at the late stage of medium- and high-dose protoscolece infections, and the proportions of effector-memory CD8+ T cells were significantly greater in the medium- (25.70% ± 4.12%) and high-dose group (28.40% ± 4.12%) than in the control group (10.50% ± 6.45%) (P < 0.05). The proportions of the central-memory CD8+ T cells were significantly higher in the high-dose group than at middle and late stages than at the early stage (P < 0.01), and the proportion of effector-memory CD8+ T cells was significantly greater in the high-dose group at the late stage than at early and middle stages (P < 0.05). The secretion of IFN-γ and IL-17A by spleen CD8+ T cells was elevated in the low- and medium-dose groups at the early stage of infection, and high-dose protoscolece infection promoted the secretion of IFN-γ and TNF-α by spleen CD8+ T cells; however, the levels of IFN-γ and TNF-α were significantly lower at the late stage than at the early and middle stages (P < 0.05). In addition, high 2B4 expression was detected in spleen CD8+ T cells in the middle- and high-dose groups at the late stage of infection, and the 2B4 expression was significantly higher in the medium(4.73% ± 1.56%) and high-dose groups (4.94% ± 1.90%) than in the low-dose group (2.49% ± 0.58%) and the control group (2.92% ± 0.60%) (P < 0.05). Conclusions E. multilocularis may be killed and eliminated through the host immune responses at the middle and late stages of low- and medium-dose protoscolece infections, while high-dose protoscolece infections may trigger the upregulation of 2B4 expression in mouse spleen CD8+ T cells at the late stage, which leads to immune exhaustion and the resultant chronic infections.
10.Analysis on the cluster epidemic of coronavirus disease 2019 in Guangdong Province
Yali ZHUANG ; Yingtao ZHANG ; Meng LI ; Min LUO ; Zhihua ZHU ; Xiaohua TAN ; Yao YI ; Xuguang CHEN ; Aiping DENG ; Huizhen ZHENG ; Min KANG ; Tie SONG ; Limei SUN
Chinese Journal of Preventive Medicine 2020;54(7):720-725
Objective:Analysis of clustering characteristics of coronavirus disease 2019 (COVID-19) in Guangdong Province.Methods:The COVID-19 cases in Guangdong Province onset from January 1 to February 29, 2020 were collected from Chinese information system for disease control and prevention and Emergency Public Reporting System. Obtain the epidemiological survey data of the cluster epidemic situation, and clarify the scale of cluster epidemic situation, the characteristics of the index cases, family and non-family subsequent cases. Calculate serial interval according to the onset time of the index cases and subsequent cases, secondary attack rate based on the close contacts tracking results, the characteristics of different cases in the clustered epidemic were compared.Results:A total of 283 cluster were collected, including 633 index cases, 239 subsequent cases. Families are mainly clustered, the total number involved in each cluster is in the range of 2-27, M( P25, P75) are 2.0 (2.0, 4.0). During January 15 to February 29, the secondary attack rate is 2.86% (239/8 363) in Guangdong Province, the family secondary attack rate was 4.84% (276/3 697), and the non-family secondary attack rate was 1.32% (61/4 632). According to the reporting trend of the number of cases in Guangdong Province, it can be divided into four stages, the rising stage, the high platform stage, the descending stage and the low level fluctuation period. The secondary attack rate of the four stages were 3.5% (140/3 987), 2.3% (55/2 399), 2.6% (37/1 435), 1.3% (7/542), respectively. The difference was statistically significant ( P=0.003). Conclusion:COVID-19 cluster mainly occurs in families in Guangdong Province. The scale of the clustered epidemic was small; the serial interval was short; and the overall secondary attack rate was low.

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