ObjectiveTo understand the seropositivity of neutralizing antibodies (NAb) and low-level NAb against SARS-CoV-2 infection in the community residents, and to explore the impact of COVID-19 vaccination and SARS-CoV-2 infection on the levels of NAb in human serum. MethodsOn the ground of surveillance cohort for acute infectious diseases in community populations in Shanghai, a proportional stratified sampling method was used to enroll the subjects at a 20% proportion for each age group (0‒14, 15‒24, 25‒59, and ≥60 years old). Blood samples collection and serum SARS-CoV-2 NAb concentration testing were conducted from March to April 2023. Low-level NAb were defined as below the 25^th percentile of NAb. ResultsA total of 2 230 participants were included, the positive rate of NAb was 97.58%, and the proportion of low-level NAb was 25.02% (558/2 230). Multivariate logistic regression analysis indicated that age, infection history and vaccination status were correlated with low-level NAb (all P<0.05). Individuals aged 60 years and above had the highest risk of low-level NAb. There was a statistically significant interaction between booster vaccination and one single infection (aOR=0.38, 95%CI: 0.19‒0.77). Compared to individuals without vaccination, among individuals infected with SARS-CoV-2 once, both primary immunization (aOR=0.23, 95%CI: 0.16‒0.35) and booster immunization (aOR=0.12, 95%CI: 0.08‒0.17) significantly reduced the risk of low-level NAb; among individuals without infections, only booster immunization (aOR=0.28, 95%CI: 0.14‒0.52) showed a negative correlation with the risk of low-level NAb. ConclusionsThe population aged 60 and above had the highest risk of low-level NAb. Regardless of infection history, a booster immunization could reduce the risk of low-level NAb. It is recommended that eligible individuals , especially the elderly, should get vaccinated in a timely manner to exert the protective role of NAb.

Objective: To retrospectively analyze the epidemic characteristics and spatial distribution of vomiting and diarrhea outbreaks in schools and kindergartens in Shanghai from 2015 to 2019, so as to provide the scientific evidence for optimizing prevention and control of vomiting and diarrhea outbreaks in schools and kindergartens. Methods: Data collection and analysis were carried out on the vomiting and diarrhea outbreaks reported to Shanghai Municipal Center for Disease Control and Prevention from 2015 to 2019. Epidemiological characteristics were analyzed and compared. The proportion and incidence of outbreaks in schools and kindergartens were calculated, and the influencing factors of outbreaks were analyzed by multivariate Logistic regression. The index of Moran s I was used for the global and local spatial auto correlation analysis. Results: Among the 344 vomiting and diarrhea outbreaks, 98.26% occurred in kindergartens, primary schools, middle schools and other educational institutions. The median number of cases per outbreak was 15. The number of suspected outbreaks and the percentage of cases involved peaked in 2015 ( 60.00% , 84.35%) and then decreased year by year to 16.00% and 38.80% in 2019. About 86.98% of the outbreaks were transmitted by human to human contact. Among the 329 outbreaks with samples collected from cases and/or environments, the main pathogen detected was norovirus ( n =280), and sapovirus was detected in outbreak for the first time in 2016. The outbreaks showed obvious seasonality, with two peaks (November, March) and one trough (July), and the majority of outbreaks occurred in primary schools (44.38%) and kindergartens (32.84%). Compared with kindergartens, the probabilities of suspected epidemic outbreaks in primary schools, combined schools, middle schools and other educational institutions were higher (adjusted OR =6.40, 9.16, 12.64 , 5.58, P <0.01). The proportion and incidence of outbreaks in educational institutions in different districts showed no high-high aggregation areas. Conclusions Primary schools and kindergartens are key places for the prevention and control of vomiting and diarrhea outbreaks. Targeted prevention and control measures should be strengthened at the beginning of each semester and before the peak of the epidemic each year. Timely reporting of symptoms, suspension of school admissions after symptoms appear and standardized disposal of vomit are effective measures to reduce interpersonal transmission and control the scale of an outbreak.

ObjectiveTo present the exploration and application of a prospective follow-up research method for acute infectious disease surveillance based on natural community populations， using COVID-19 infection as an example， and to provide a reference for improving the infectious disease surveillance and early warning system. MethodsA multi-stage probability proportional sampling method was employed to sample residents from all communities of 16 administrative districts in Shanghai， with households as the units. A cohort for acute infectious diseases based on natural community populations was established. The baseline survey was conducted for all cohort subjects， and COVID-19 antigen test kits were distributed. From December 21， 2022 to September 30， 2023， prospective follow-up monitoring of COVID-19 antigen and nucleic acid was carried out on the study subjects on a weekly basis. The baseline characteristics and follow-up information of the cohort subjects were described. ResultsThe cohort for acute infectious diseases included a total of 12 881 subjects， comprising 6 098 males （47.3%） and 6 783 females （52.7%）. The baseline survey revealed that 35.2% （4 540/12 881） of the subjects had a history of COVID-19 infection. During the follow-up period from December 21， 2022 to September 30， 2023， the average incidence density in the cohort was 0.61/person-year， with a higher incidence density in females （0.63/person-year） compared to males （0.59/person-year）. Individuals aged 60 and above （0.64/person-year） and those with underlying health conditions （0.67/person-year） had a higher incidence density. Healthcare workers showed a notably higher incidence density （0.84/person-year） than that in other occupational groups. As of September 30， 2023， a total of 340 subjects in the cohort experienced secondary infections， with a median interval of 170 days between the first and second infections. ConclusionThis study applies cohort study method to acute infectious disease surveillance， providing crucial data support for estimating infection rates and forecasting alerts for acute infectious diseases in the community. This method can be promoted and applied as a new approach for acute infectious disease surveillance.

Objective:To evaluate the performance of the influenza surveillance network and compare the epidemic intensity of influenza during 2014-2020 in Shanghai.Methods:Based on the weekly reports of influenza-like illness (ILI) and laboratory-confirmed influenza cases from January 1, 2014 to December 31, 2020. This study first evaluated the data reporting and specimen collection of ILI cases for each sentinel hospital, and then calculated the percentage of ILI (ILI%), the proportion of specimens tested positive for influenza, and the incidence of influenza among all ILI outpatient and emergency visits to measure the epidemic intensity of influenza. Finally, seasonal autoregressive integrated moving average (ARIMA) model was applied to quantify the changes in epidemic intensity of influenza in 2020.Results:The proportion of influenza surveillance sentinel hospitals with a score of less than 5 in the evaluation of ILI data reporting and samples collection were 9.68% and 21.05% in 2020 in Shanghai, respectively. ILI% was estimated to be 1.51% (95% CI: 1.50%-1.51%) and 2.31% (95% CI: 2.30%-2.32%), respectively for 2014-2019 and 2020; the proportion of specimens tested positive was 24.27% (95% CI: 24.02%- 24.51%) and 7.15% (95% CI: 6.78%-7.54%), respectively; and the incidence of influenza was 3.66‰ (95% CI: 3.62‰-3.70‰) and 1.65‰ (95% CI: 1.57‰-1.74‰), respectively. ARIMA model showed that ILI% was increased by 45.25% in 2020 in Shanghai, and the proportion of specimens tested positive and the incidence of influenza were reduced by 78.45% and 51.80%, respectively. Conclusions:In 2020, the performance of influenza surveillance system has changed, ILI% has increased, the proportion of specimens tested positive and the incidence of influenza has decreased in Shanghai. The change in the quality of influenza surveillance is also a potential factor affecting the epidemic intensity of influenza. In the future, the quality control of influenza surveillance network still needs to be further strengthened.

Objective:To study the infection status and epidemiological characteristics of parainfluenza virus (PIV) in acute respiratory tract infection adult cases in Shanghai from 2015 to 2021, and to provide a scientific basis for preventing and controlling PIV.Methods:Acute respiratory tract infections were collected from 13 hospitals in Shanghai from 2015 to 2021. Relevant information was registered, and respiratory specimens were sampled to detect respiratory pathogens by multiplex PCR.Results:A total of 5 104 adult acute respiratory tract infection cases were included; the overall positive rate of the respiratory pathogens was 29.37% (1 499/5 104). The positive rate of PIV was 2.61% (133/5 104), compared with 2.32% (55/2 369) and 2.85% (78/2 735) in influenza-like cases (ILI) and severe acute respiratory infection (SARI) cases, respectively. Among them, PIV3 accounted for the highest proportion (62.41%, 83/133), followed by PIV1 (18.80%, 25/133), PIV2 (9.77%, 13/133), and PIV4 (9.02%, 12/133). The incidence of PIV-positive cases was mainly distributed in the first and second quarters, accounting for 62.41% (83/133). The difference in the incidence in each quarter was significant ( χ2=24.78, P<0.001). Mixed infection accounted for 18.80% (25/133) of 133 PIV-positive cases, the mixed infection rates of ILI and SARI were 18.18% (10/55) and 19.23% (15/78), respectively, and the main mixed pathogen of PIV was coronavirus 229E. Conclusions:There are a certain proportion of PIV-positive acute respiratory tract infection cases in Shanghai. It is necessary to strengthen the etiological surveillance in acute respiratory tract infection cases, especially the mixed infection of PIV and other pathogens.

Objective:To analyze the features of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) co-infected with other common respiratory pathogens among coronavirus disease 2019 (COVID-19) patients in Shanghai City, and to provide a reference for scientific prevention and control of COVID-19 and other respiratory infectious diseases.Methods:Descriptive epidemiological approaches were used to analyze the data of COVID-19 reported cases in Shanghai City from January 2020 to February 2021 in the information system of Chinese Disease Prevention and Control. Clinical data of the participants were collected, and their SARS-CoV-2 nucleic acid-positive respiratory specimens were collected at the time of illness onset or admission. Multiplex reverse transcription-polymerase chain reaction (RT-PCR) was performed to detect the 22 respiratory pathogens. Independent-samples t test was used for statistical analysis. Results:Of the 272 patients with COVID-19, 15(5.5%) had co-infection of SARS-CoV-2 with other respiratory pathogens, all of which were double infection. There were three cases infected with enterovirus/rhinovirus, two of each with adenovirus, human metapneumovirus and coronavirus NL63/HKU1, and one of each with coronavirus 229E, influenza A virus H1N1, parainfluenza virus 1 and respiratory syncytial virus B. Two cases infected with Mycoplasma pneumoniae. Among the 272 COVID-19 patients, 212(77.9%) had fever, 117(43.0%) had cough, 46(16.9%) had fatigue, and 35(12.9%) had sore throat. The white blood cell count of co-infection cases was higher than that of non-co-infection cases ((6.8±1.7)×10 9/L vs (5.3±1.6)×10 9/L), and the difference was statistically significant ( t=3.09, P=0.008). Conclusions:There is a certain proportion of co-infection of SARS-CoV-2 with other respiratory pathogens among the COVID-19 cases in Shanghai City, mainly viral pathogens, especially enterovirus/rhinovirus. A rational combination of drugs was recommended to improve the cure rate. Surveillance of acute respiratory infection should be further strengthened as well.

Objective:To analyze the changes in the epidemiological characteristics of scarlet fever cases in Shanghai City before and after the outbreak of coronavirus disease 2019 (COVID-19), and to provide a reference for scientific prevention and control of scarlet fever.Methods:The information of scarlet fever reported cases in Shanghai City from January 2016 to June 2021 in the information system of Chinese Disease Prevention and Control was collected, and the differences in time trend, regional distribution, age and gender distribution of cases before and after the outbreak of COVID-19 in Shanghai City were analyzed by descriptive epidemiologic method.Results:The incidence rate of scarlet fever reported in 2016-2019 was (0.22-4.02)/100 000 in each month, with a median of 1.13/100 000. During January 2020 (the outbreak began in Shanghai City) and June 2021, the incidence rate of scarlet fever was (0.01-1.64)/100 000, with a median of 0.14/100 000, which was 12.39% of that before the outbreak of COVID-19. During February and June 2020, the monthly reported incidence rate of scarlet fever was (0.18-0.58)/100 000, showing an upward trend compared with the same period in 2020 ((0.01-0.05)/100 000). From 2016 to 2019, the annual reported incidence rate of each district was (0.55-65.48)/100 000, with a median of 9.57/100 000; while in 2020, the annual reported incidence rate of each district was (0.29-9.85)/100 000, with a median of 2.18/100 000, which was 22.78% of that before the outbreak of COVID-19. The incidence of scarlet fever dropped significantly. The incidence rate in Minhang District was still the highest. The cases were mainly four to eight years old, and there was no substantial difference of the proportions before and after COVID-19 pandemic, with the incidence rate of six years old group the highest. The proportion of male was more than female in reported case, while the male ratio in reported cases was not significantly different before and after COVID-19 pandemic.Conclusions:The incidence rate of scarlet fever in Shanghai City has dropped sharply after COVID-19 pandemic. The main epidemiological characteristics of the regional and population distribution of cases remain unchanged.

Objective:To study the epidemiological characteristics and mixed infection of adenovirus in acute respiratory tract infections in Shanghai from 2015 to 2019, and to provide scientific basis for the prevention and control of adenovirus.Methods:Acute respiratory tract infections were collected from 3 hospitals in Shanghai from 2015 to 2019. Relevant information was registered and respiratory specimens were sampled for detection of respiratory pathogens by multiplex PCR.Results:A total of 1 543 cases of acute respiratory tract infection were included. The positive rate of adenovirus was 2.92%(45/1 543), the positive rates of influenza like illness (ILI) and severe acute respiratory illness (SARI) were 2.74%(29/1 058) and 3.30%(16/485), respectively. The positive rate of ILI during January-May 2019 was 5.43%(7/129), higher than that in the same period of 2015- 2018 (0.52%-4.48%) (Fisher’s exact test value=8.92, P=0.036). The incidence of adenovirus-positive cases was mainly distributed in the first and second quarters, accounting for 62.22% (28/45). The difference of the incidence of adenovirus-positive cases in each quarter was significant ( χ2= 12.52, P=0.006). The positive rate in the second quarter was highest (6.03%), which was higher than that in other quarters (1.89%-2.93%). There were significant differences among different age groups ( χ2=16.94, P=0.001), and the positive rate decreased with age ( χ2=10.16, P=0.001). The positive rate of 13-19 years old group (9.43%) was higher than that of other age groups (1.48%-4.81%). The positive rate of student group (12.07%) was higher than that of other occupations (2.61%). The difference was systematic ( χ2=11.53, P=0.001). Mixed infection accounted for 31.11% (14/45) of 45 adenovirus positive cases. The mixed infection rates of ILI and SARI were 34.48% (10/29) and 25.00% (4/16), respectively. Among 14 cases of mixed infection, the main mixed infection pathogens of adenovirus were influenza A virus and coronavirus. Conclusion:Adenovirus surveillance should be further strengthened in adolescents with a focus on students and other key groups in the second quarter.

Shanghai Municipal Center for Disease Control and Prevention has implemented an active comprehensive surveillance project of acute respiratory infections in adults in Shanghai, including influenza like illness (ILI) and severe acute respiratory infection (SARI). By testing and identifying a variety of respiratory pathogens, it was found that influenza viruses were the main pathogens in 172 ILI cases in 2019. The positive rates of influenza A (H1N1) pdm09 virus, influenza A (H3N2) virus and influenza B virus Victoria lineage were 30.81%, 14.53% and 30.55%, respectively. The positive detection of influenza A (H1N1) pdm09 virus peaked in the first quarter. The positive rate of enterovirus/human rhinovirus was 6.40%, with a positive detection peak in the third quarter, while the positive rate of adenovirus was 4.65% with a positive detection peak in the second quarter of the year. Two human coronavirus (HCoV)-OC43 positive samples, 1 HCoV-HKU1 positive sample and 1 HCoV-NL63 positive sample were detected, respectively, and no HCoV-229E positive sample was detected. The detection rate of Staphylococcus aureus was 17.44%, and the detection rate of Klebsiellapneumoniae was 9.88%. Influenza viruses were also the main pathogens in 1 447 SARI cases. The positive rates of influenza A (H1N1) pdm09 virus, influenza A (H3N2) virus and influenza B virus Victoria lineage were 5.46%, 1.73% and 0.30%, respectively. The positive detection of influenza A (H1N1) pdm09 virus (17.50%) peaked in the first quarter. The total positive detection rate of enterovirus/human rhinovirus was 2.97%, the positive detection peaked in the first quarter. The positive rate of Mycoplasma pneumoniae was 3.25% and the positive rate of Legionella was 1.04%. 5 HCoV-229E positive samples, 10 HCoV-OC43 positive samples, 7 HCoV-HKU1 positive samples and 6 HCoV-NL63 positive samples were detected. Eight strains of Staphylococcus aureus, 4 strains of Pseudomonas aeruginosa and 3 strains of Klebsiella pneumoniae were detected after cultures. By implementing the active surveillance, we not only detected a case of human infection with avian influenza A(H7N9) virus in time, but also preliminary understood the pathogenic spectrum characteristics and seasonality of ILI and SARI in Shanghai. In recent years, the surveillance methods have been continuously improved and the number of sentinel hospitals has increased gradually. In particular, for the response to COVID-19, the Surveillance Information Reporting System of Acute Respiratory Infection based on HIS system has been promoted to cover the whole city, which might lay a foundation for the active surveillance and early warning of emerging infectious diseases in the future.

Objective: To analyze the etiologic and epidemiological characteristics of adult acute respiratory infections in Shanghai during 2015-2017. Methods: Data was collected from outpatients with acute respiratory infections who visited the Fever Clinics in three hospitals of different levels in three administrative regions of Shanghai, from 2015 to 2017. Basic information and nasopharyngeal swabs were collected from cases in line with the inclusion criteria. Multiplex RT-PCR and bacterial cultures were performed to detect the respiratory pathogens. Results: A total of 806 individuals were enrolled from 2015 to 2017. Respiratory pathogens were identified in 73.45% (592/806) of the cases, with the virus detection rate as 66.75% (538/806). It was found that the major respiratory pathogens for virus detection were influenza A in 326 (40.45%), influenza B in 116 (14.39%), rhinovirus/enterovirus in 39 (4.84%) of the cases. The overall detection rate of bacteria was 16.13% (130/806), including Klebsiella pneumoniae in 90 (11.17%) cases, Staphylococcus Aureus in 46 (5.71%) cases. Other kind of bacteria were not detected in our study. The detection rates on Mycoplasma pneumoniae was 5.33% (43/806) and on Chlamydia pneumonia was 0.37% (3/806). Co-infection with multiple pathogens was detected in 18.61% (150/806) of the cases, including 135 with double infection (accounting for 90.00%), 14 with triple infection and 1 with quadruple infection (accounted for 9.33% and 0.67%, respectively). Among the 150 cases with co-infections, the main identified pathogens were influenza A, Klebsiella pneumoniae, Staphylococcus aureus, and Mycoplasma pneumoniae. Pathogens of acute respiratory infections that identified among the outpatients from the Fever Clinics at different time, region or population, the characteristics were different (P<0.001). Conclusions In 2015-2017, outpatients with acute respiratory infections in Shanghai were mainly caused by influenza virus or other viruses, however dynamically with its composition, time, region and characteristics of the population. It is necessary to strengthen and combine related medical and preventive services and to develop the appropriate strategies regarding clinical diagnosis and treatment.