Analysis of epidemiological characteristics of the clustered cases of hand， foot and mouth disease in Pudong New Area， Shanghai， 2017‒2022 / 上海预防医学

ObjectiveTo analyze the epidemiological characteristics and etiology of clustered outbreaks of hand， foot， and mouth disease （HFMD） in Pudong New Area， Shanghai from 2017 to 2022， and to provide a scientific basis for the prevention and control of HFMD in the area. MethodsThe data related to HFMD clustered outbreaks from 2017 to 2022 were obtained from the Pudong New Area HFMD outbreak database. Descriptive analysis was conducted to explore the outbreak scope， seasonal characteristics， distribution of occurrence settings， and etiological composition. ResultsFrom 2017 to 2022， Pudong New Area reported a total of 2 547 HFMD clusters， involving 8 884 cases， with an average of 3.49 cases per event. The majority of events （78.52%） had between 2 and 4 cases. The peak reporting periods for clustered HFMD from 2017 to 2019 and in 2021 were during the summer （May‒July） and autumn （September‒November）. The seasonal pattern was less distinct in 2020 and 2022， likely due to the impact of the COVID-19 pandemic. The majority of clustered outbreaks occurred in childcare facilities （44.64%）， followed by households/neighborhood committees （44.21%）， with schools accounting for a smaller proportion （12.39%）. The etiology revealed the coexistence of multiple enterovirus genotypes， with a positive detection rate of 60.46%， and CoxA6 being the dominant strain. ConclusionHFMD clustered outbreaks in Pudong New Area show fluctuating trends， with significant yearly differences in the number of incidents. The predominant seasons for outbreaks are summer and autumn， with CoxA6 identified as the dominant strain. The implementation of prevention and control measures for COVID-19 significantly reduced the occurrence of HFMD outbreaks. Continuous monitoring and focus on large-scale clustered outbreaks in key institutions are essential for the future.

Epidemiological characterization of a cluster of COVID-19 caused by SARS-CoV-2 Omicron variant at a construction site in Qingpu District， Shanghai / 上海预防医学

ObjectiveTo determine the epidemiological characteristics of a cluster of SARS-CoV-2 Omicron variant at a construction site and provide evidence for further COVID-19 prevention and control. MethodsDemographic data of all COVID-19 cases at a construction site in Qingpu District， Shanghai， and basic information of the construction site were retrospectively collected through filed investigation. Descriptive epidemiology was used for the analysis. Basic reproduction number （R0） and time-dependent reproduction number （Rt） were calculated using R program. ResultsDuring April 12 and May 8， 2022， a total of 314 cases were reported at the construction site， with an attack rate of 60.62%. The attack rate significantly differed between workers and managers （χ2=10.868， P<0.001）， whereas did not differ statistically by gender （χ2=0.358， P=0.550） or by vaccination status （χ2=2.861， P=0.091）. The age of all cases ranged from 5 months of age to 68 years， with a media age of 49.0 years （interquartile range： 39.8， 54.0）. In all cases， male was predominant （83.44%）. Moreover， the epidemic was mainly concentrated in the workers’ dormitory area， with infected cases identified in all buildings of each dormitory area. The attack rate ranged between 33.33% and 87.50% across the buildings. Symptoms and signs were observed among 43.0% of all cases， of which major clinical manifestations included cough （33.33%）， fever （30.37%） and headache （17.04%）. Clinical manifestations did not differ by gender （χ2=1.275， P=0.259） or by vaccination status （χ2=0.186， P=0.666）. Additionally， R0 was estimated to be 6.08 （95% confidence interval： 4.49‒8.02）. The Rt showed a decline in the beginning， followed by an increase and a re-decline. ConclusionThe cluster epidemic of COVID-19 caused by Omicron variant at the construction site is highly contagious， spreads rapidly and quietly， causes mild symptoms， which finally resulted in a large number of infected cases. It warrants rapid and strict containment when an epidemic occurs at construction sites.

Temporal dynamics of SARS-CoV-2 genome mutations that occurred in vivo on an aircraft.

We analyzed variations in the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genome during a flight-related cluster outbreak of coronavirus disease 2019 (COVID-19) in Shenzhen, China, to explore the characteristics of SARS-CoV-2 transmission and intra-host single nucleotide variations (iSNVs) in a confined space. Thirty-three patients with COVID-19 were sampled, and 14 were resampled 3-31 days later. All 47 nasopharyngeal swabs were deep-sequenced. iSNVs and similarities in the consensus genome sequence were analyzed. Three SARS-CoV-2 variants of concern, Delta (n = 31), Beta (n = 1), and C.1.2 (n = 1), were detected among the 33 patients. The viral genome sequences from 30 Delta-positive patients had similar SNVs; 14 of these patients provided two successive samples. Overall, the 47 sequenced genomes contained 164 iSNVs. Of the 14 paired (successive) samples, the second samples (T2) contained more iSNVs (median: 3; 95% confidence interval [95% CI]: 2.77-10.22) than did the first samples (T1; median: 2; 95% CI: 1.63-3.74; Wilcoxon test, P = 0.021). 38 iSNVs were detected in T1 samples, and only seven were also detectable in T2 samples. Notably, T2 samples from two of the 14 paired samples had additional mutations than the T1 samples. The iSNVs of the SARS-CoV-2 genome exhibited rapid dynamic changes during a flight-related cluster outbreak event. Intra-host diversity increased gradually with time, and new site mutations occurred in vivo without a population transmission bottleneck. Therefore, we could not determine the generational relationship from the mutation site changes alone.

Epidemiological characteristics of hand, foot and mouth disease clusters in kindergartens and schools in Jinshan District / 预防医学

Objective@#To investigate the epidemiological characteristics of clusters of hand, foot and mouth disease (HFMD) in kindergartens and schools in Jinshan District, Shanghai Municipality from 2016 to 2021, so as to provide insights into improving the prevention and control measurements of HFMD in Jinshan District.@*Methods@#Data of HFMD cases in Jinshan District from 2016 to 2021 were collected through Chinese Disease Prevention and Control Information System, and data pertaining to HFMD clusters in kindergartens and schools were also collected. The scale, temporal distribution, regional distribution and distribution of cluster places were descriptively analyzed. @*Results@#Totally 338 HFMD clusters involving 974 cases were identified in kindergartens and schools in Jinshan District from 2016 to 2021, with an average attack rate of 9.89%. The number of cases in each cluster ranged from 2 to 12 cases, with a median number of 2 (interquartile range, 1) cases, and there were 223 clusters involving 2 cases, accounting for 65.98%. The duration of clusters ranged from 1 to 16 days, with a median duration of 4 (interquartile range, 3) days. HFMD peaked from April to June (136 clusters, 40.24%) and from September to December (176 clusters, 52.07%). All the 11 streets and towns (high-tech zones) were reported HFMD clusters, and the three largest number of clusters were reported in Zhujing Town (72 clusters, 21.30%), Shanyang Town (63 clusters, 18.64%) and Tinglin Town (40 clusters, 11.83%). There were 268 HFMD clusters in kindergartens (79.29%) and 70 in schools (20.71%), and the prevalence of HFMD clusters was higher in kindergartens than in schools (35.51% vs. 17.03%; χ2=31.507, P<0.001). @*Conclusions@#HFMD clusters in kindergartens and schools showed seasonal characteristics from 2016 to 2021 in Jinshan District, which predominantly occurred in Zhujing Town, Shanyang Town and Tinglin Town, and kindergartens were the main places.

Epidemiological characteristics of 45 norovirus clusters in Baoshan District / 预防医学

Objective@#To investigate the epidemiological characteristics of 45 norovirus clusters in Baoshan District, Shanghai Municipality from 2019 to 2021, so as to provide the evidence for improving the management of norovirus clusters. @*Methods@#The epidemiological characteristics and laboratory testing of 45 norovirus clusters were collected in Baoshan District from 2019 to 2021, and the temporal distribution, population distribution, distribution of places of norovirus clusters, clinical manifestations, laboratory testing results, origin of norovirus infection and transmission routes of norovirus clusters were analyzed using a descriptive epidemiological method. @*Results@#A total of 45 norovirus clusters involving 29 379 individuals were reported in Baoshan District from 2019 to 2021, and 435 cases with norovirus infections were identified, with an average attack rate of 1.48%. Norovirus infection most often occurred from November to April of the following year, and the infection predominantly occurred among students (408 cases, 93.79%). There were 25 norovirus clusters in kindergartens (55.56%), 18 clusters in primary and middle schools (40.00%), one cluster in a social care facility and one cluster in a geriatric ward. Vomiting was the predominant clinical symptom (416 cases, 95.63%). The positive rate of norovirus was 37.35% in 597 samples. There were 40 norovirus clusters caused by the norovirus GⅡ genotype (88.89%), and the median duration of the norovirus cluster was 6 days (interquartile range, 1 day). In addition, 82.22% of the norovirus clusters reported to centers for disease control and prevention within 1 day,and 88.89% of the clusters were transmitted through human to human transmission or vomitus of cases.@*Conclusion@#The norovirus clusters predominantly occur in winter/spring and among students in Baoshan District from 2019 to 2021. Kindergartens and primary and middle schools are main places of norovirus infections, and the norovirus GⅡ genotype is the main type of pathogens. Human-to-human transmission and exposure to patients' vomitus are the main routes of transmission.

Epidemiological investigation of a school COVID-19 outbreak in Shanghai / 上海预防医学

ObjectiveTo describe a COVID-19 outbreak due to SARS-CoV-2 Omicron variant in a school and provide suggestions for COVID-19 prevention and control. MethodsData on the COVID-19 outbreak in a school in Putuo District of Shanghai were collected from November 14 to December 20， 2022. Epidemiological characteristics， incidence rate of secondary cases and response measures were described and analyzed. ResultsA total of 27 COVID-19 cases were identified infected with SARS-CoV-2 Omicron BA.5.2 variant， including 14 students （51.9%） and 13 family members / teachers living with those students （48.1%）. The first case occurred on November 14， with peak incidence during November 16-18. The median generation interval of the second generation cases was 2 （2，3） days. The index case （case 1， a student） had a clear contact history outside the school， which was found through routine examination in key populations in the school. Immediate management was conducted after the notification. All the second generation cases were exposed students in the same class with case 1， which were identified during the quarantine， whereas the third generation cases were their family members/teachers living with the second generation cases. The incidence rate within the class and school were 36.8% and 3.0%， respectively. No further social transmission was found outside the school. ConclusionEarly detection， multi-sectoral collaboration， prompt control and quarantine measures are effective in containing SARS-CoV-2 transmission. Health promotion， surveillance， ventilation and prophylactic disinfection should be reinforced in schools， office buildings and other gathering places.

Risk Transmission Mechanism of Domestic Cluster Epidemic Caused by Overseas Imported Cases: Multiple Case Studies Based on Grounded Theory.

The continued severity of the global epidemic situation has led to a rising risk of imported cases in China, and domestic cluster epidemic events caused by imported cases have occurred from time to time, repeatedly causing nation-wide disruption. To deeply explain this phenomenon, this study adopted the grounded theory method, using the 5·21 Guangzhou COVID-19 outbreak and 7·20 Nanjing COVID-19 outbreak as examples to study the risk transmission mechanism of domestic cluster epidemic caused by overseas imported cases. The study found that the risk factors for the phenomenon mainly include the following seven aspects: external protection, operations and supervision, international and domestic environment, contaminated objects, virus characteristics, management efficacy, and individual factors. These risk factors together constitute the "detonator", "risk source", "risk carrier," and "risk amplifier" in the risk transmission process. In addition, this study also found that the transmission mechanism of domestic clusters caused by imported cases is a process of secondary risk amplification. The increase in risk carriers leads to a surge in secondary risks compared with the first, which leads to the outbreak of domestic clusters. Finally, based on the characteristics of the transmission mechanism and risk transmission components, this study provides some suggestions on risk mitigation for public departments to optimize China's epidemic prevention policies.

[Investigation on two family clusters of COVID-19 in a county of Baotou city in Inner Mongolia Autonomous Region].

Objective: To investigate the epidemiological characteristics and transmission chain of COVID-19 in two families, and to provide scientific evidence for effective prevention and control measures. Methods: Field epidemiological investigation was conducted for the COVID-19 cases occurred in two families and the close contacts in a county of Baotou city in Inner Mongolia Autonomous Region. Descriptive statistical analysis on epidemiological data was conducted. Results: The infection source of the COVID-19 cases in the two families was a man who had living history in Wuhan. After his return, his parents were infected by him. A few days later, the members of a neighbor family were found to be infected, and relatives of this family were also infected after dining together repeatedly. Finally, ten confirmed cases and three suspected cases of COVID-19 were detected in the two families. Conclusions: Human-to-human transmission of COVID-19 can occur not only in a family but also in neighborhoods. The cases in two families had close relationship, indicating the necessity to strengthen the health education about COVID-19 prevention and control and the management of groups at high risk to reduce the incidence of COVID-19 in families and neighborhoods.

[Contagiousness and secondary attack rate of 2019 novel coronavirus based on cluster epidemics of COVID-19 in Guangzhou].

Objective: To analyze the contagiousness and secondary attack rate of 2019 novel coronavirus in cluster epidemics in Guangzhou and provide evidence for the prevention and control of COVID-19. Methods: All the individuals identified to be infected with 2019-nCoV in Guangzhou, including confirmed cases and asymptomatic cases, were included and classified as imported cases and local cases. The first case of each cluster epidemic was defined as index case, and the number of subsequent infections was calculated to evaluate the contagiousness and secondary attack rate of 2019 novel coronavirus in the shortest incubation period of 1-3 days. Results: As of 18 February, 2020, a total of 349 cases of 2019-nCoV infection, including 339 confirmed cases (97.13%) and 10 asymptomatic cases (2.87%) were reported in Guangzhou. There were 68 clusters involving 217 2019-nCoV infection cases (210 confirmed cases and 7 asymptomatic cases). The median number of subsequent infections caused by an index case in a cluster epidemic was 3, among which 2 were confirmed cases and 1 was asymptomatic cases, respectively. The average number of contagiousness was 2.18 in shorted incubation period of 1-3 days (The average number of infected cases were 2.18 cases by the index case in a cluster epidemic), the average infection number in family members was 1.86, and the infection ratio of family member transmission was 85.32% (1.86/2.18). The secondary attack rate in close contacts with shortest incubation period of 1-3 days was 17.12%-18.99%, the secondary attack rate in family members was 46.11%-49.56%. Conclusions: The cluster epidemic of COVID-19 in Guangzhou mainly occurred in families, the contagiousness was high. It is necessary to strengthen the prevention and control to reduce the community transmission of COVID-19.

[Investigation on a cluster epidemic of COVID-19 in a supermarket in Liaocheng, Shandong province].

Objective: To explore clustered epidemic of COVID-19 in Liaocheng city and analyze infection status and chain of transmission of the cases. Methods: A joint investigation team of emergency response for COVID-19 epidemic by CDC professional workers of Liaocheng city and district at two levels on January 30, 2020. According to a indicator case from ZH supermarkets, close contacts and related subjects were tracked and screened on February 1, including ZH supermarket employees, family members having contact history with related cases during January 13-26, supermarket clients during January 16-30 and family members of related cases. an epidemiological investigation was carried on and their swab of nose/throat were collected and were sent to Liaocheng CDC laboratory, real-time fluorescence quantitative RT-PCR was used to detect nucleic acids of SARS-CoV-2. Results: a total of 8 437 people were screened during January 30 to February 9, 2020 (120 employees of supermarket, 93 family members, and 8224 clients of supermarket). The epidemic was caused by ZH cases and brought clustered cases in four families. A total 25 cases of SARS-CoV-2 infection, the total infection rate of subjects was 0.30% (25/8 437) with 22 confirmed cases (0.26%, 22/8 437) and 3 asymptomatic patients (0.04%, 3/8 437), asymptomatic patients accounted for 12.00% (3/25) of all infection cases. The infection rates of supermarket employees, family members of confirmed cases and supermarket clients were 9.17% (11/120), 12.90% (12/93) and 0.02% (2/8 224). Conclusions: This was a cluster epidemic caused by one imported case of COVID-19 in a supermarket of Liaocheng city. Prevention and control of cluster epidemic should be focused on chain of community transmission and family cluster cases. It must also be an attention for transmission risk of asymptomatic patients.

[Epidemiological investigation on a cluster epidemic of COVID-19 in a collective workplace in Tianjin].

Objective: To investigate and analysis the epidemiological characteristics of a cluster epidemic of COIVD-19 in a collective workplace in Tianjin, evduate the prevention and control measures based on limited evidence and experience in early period of COVID-19 epidemic. Methods: Descriptive research method was used to describe the distribution and other epidemiological characteristics of the cluster cases of COVID-19. Results: Since the onset of the first index case on January 15, ten confirmed COVID-19 cases had occurred in the workplace, and the epidemic had spread from the workplace to 4 families, infecting 7 family members. The median age of 17 cases was 55 (19-79) years. All the 10 employee cases were males, and in the family cases, 3 were males and 4 were females. Of the employee cases, 8 worked in CW workshop and 2 worked in administrative office building. The median exposure-onset interval of all the cases was 4 days, and the median exposure-onset interval was 4.5 days in the employee cases and 4 days in the family cases. The median onset-medical care seeking interval was 4 days in the non-isolated cases, 2.5 days in the cases with home isolation after onset, and 0.5 day in the cases with home isolation before onset. Conclusions: The clustering of COVID-19 cases was observed in this workplace in Tianjin, which affected 4 families. In the early stage of the epidemic, accurate and rapid blocking and control measures can completely prevent the large-scale spread of COVID-19.

Epidemiological investigation on a cluster epidemic of COVID-19 in a collective workplace in Tianjin / 中华流行病学杂志

Objective To investigate and analysis the epidemiological characteristics of a cluster epidemic of COIVD-19 in a collective workplace in Tianjin, evduate the prevention and control measures based on limited evidence and experience in early period of COVID-19 epidemic. Methods Descriptive research method was used to describe the distribution and other epidemiological characteristics of the cluster cases of COVID-19. Results Since the onset of the first index case on January 15, ten confirmed COVID-19 cases had occurred in the workplace, and the epidemic had spread from the workplace to 4 families, infecting 7 family members. The median age of 17 cases was 55 (19-79) years. All the 10 employee cases were males, and in 7 family cases, 3 were males and 4 were females. Of the employee cases, 8 worked in CW workshop and 2 worked in administrative office building. The median exposure-onset interval of all the cases was 4 (0-12) days, and the median exposure-onset interval was 4.5 days in the employee cases and 4 days in the family cases. The median onset-medical care seeking interval was 4 days in the non-isolated cases, 2.5 days in the cases with home isolation after onset, and 0.5 day in the cases with home isolation before onset. Conclusion The clustering of COVID-19 cases was observed in this workplace in Tianjin, which affected 4 families. In the early stage of the epidemic, accurate and rapid blocking and control measures can completely prevent the large-scale spread of COVID-19.

Reflections on the Cluster Epidemic of COVID-19; Lessons Learned from Wuhan's Experience: A Brief Review.

At present, new coronavirus pneumonia (COVID-19) is circulating worldwide. The pathogen of this coronavirus pneumonia is named SARS-CoV-2. The virus has a long incubation period and is highly contagious. There is currently no specific targeted drug treatment. The focus of anti-epidemic work should be more on prevention and control while cutting off the virus transmission route while treating infected patients, and protecting healthy people. In order to protect the safety and health of the Chinese citizens and to maintain the safety of world public health, the Chinese government and people have made unprecedented efforts to control the epidemic. Many people in the international community have joined in limiting the spread of COVID-19. This article combines the development of COVID-19 epidemic situation in Wuhan, the relevant prevention and control measures of the Wuhan government and local health authorities to share Wuhan's experience on control the cluster epidemic and provide new suggestions and ideas for epidemic prevention and control.