BACKGROUND:As tissue engineering brings new hope to the worldwide problem of articular cartilage repair,the construction of light-curing 3D printed hydrogel scaffolds with biomimetic composition is of great significance for cartilage tissue engineering. OBJECTIVE:To construct a biomimetic methacryloylated hyaluronic acid/acellular Wharton's jelly composite hydrogel scaffold by digital light processing 3D printing technology,and to evaluate its biocompatibility. METHODS:Wharton's jelly was isolated and extracted from human umbilical cord,then decellulated,freeze-dried,ground into powder,and dissolved in PBS to prepare 50 g/L acellular Wharton's jelly solution.Methylallylated hyaluronic acid was prepared,lyophilized and dissolved in PBS to prepare 50 g/L methylallylated hyaluronic acid solution.Acellular Wharton's jelly solution was mixed with methacrylyacylated hyaluronic acid solution at a volume ratio of 1:1,and was used as bio-ink after adding photoinitiator.Methylacrylylated hyaluronic acid hydrogel scaffolds(labeled as HAMA hydrogel scaffolds)and methylacrylylated hyaluronic acid/acellular Wharton's jelly gel scaffolds(labeled as HAMA/WJ hydrogel scaffolds)were prepared by digital light processing 3D printing technology,and the microstructure,swelling performance,biocompatibility,and cartilage differentiation performance of the scaffolds were characterized. RESULTS AND CONCLUSION:(1)Under scanning electron microscope,the two groups of scaffolds showed a three-dimensional network structure,and the fiber connection of HAMA/WJ hydrogel scaffold was more uniform.Both groups achieved swelling equilibrium within 10 hours,and the equilibrium swelling ratio of HAMA/WJ hydrogel scaffold was lower than that of HAMA hydrogel scaffold(P＜0.05).(2)CCK-8 assay showed that HAMA/WJ hydrogel scaffold could promote the proliferation of bone marrow mesenchymal stem cells compared with HAMA hydrogel scaffold.Dead/live staining showed that bone marrow mesenchymal stem cells grew well on the two groups of scaffolds,and the cells on the HAMA/WJ hydrogel scaffolds were evenly distributed and more cells were found.Phalloidine staining showed better adhesion and spread of bone marrow mesenchymal stem cells in HAMA/WJ hydrogel scaffold than in HAMA.(3)Bone marrow mesenchymal stem cells were inoculated into the two groups for chondrogenic induction culture.The results of qRT-PCR showed that the mRNA expressions of agglutinoglycan,SOX9 and type Ⅱ collagen in the HAMA/WJ hydrogel scaffold group were higher than those in the HAMA hydrogel scaffold group(P＜0.05,P＜0.01).(4)These findings indicate that the digital light processing 3D bioprinting HAMA/WJ hydrogel scaffold can promote the proliferation,adhesion,and chondrogenic differentiation of bone marrow mesenchymal stem cells.

Objective:To analyze the performance of emergency response to 2019 novel coronavirus (2019-nCoV) positive cases in an international test competition in an Winter Olympic Game venue and provide evidences for the COVID-19 prevention and control in similar competitions.Methods:A retrospective analysis on the epidemiological investigation and nucleic acid test results of the cases, the implementation of prevention and control measures, including the communication with sport teams and others, was conducted.Results:The positive cases of 2019-nCoV among entering people were detected before entry, at airport, hotel and venue. Two positive cases were reported before entry, 2 positive cases infected previously and 3 asymptomatic cases were reported after the entry. The venue public health team and local CDC conducted epidemiological investigation and contact assessment jointly in a timely and efficient manner. No local secondary transmission occurred, but the nucleic acid test results of positive persons fluctuated, posing serious challenges to the implementation of prevention and control measures.Conclusion:In large scale international competition, there is high risk of imported COVID-19. It is necessary to fully consider the fluctuation of nucleic acid test results, the criteria for determination and cancellation of positive results and give warm care to positive cases in the emergency response.

Objective:To provide evidence for clinical diagnosis, prevention and control of group A rotavirus (RVA) diarrhea, the clinical characteristics of RVA diarrhea in children in Beijing from 2011 to 2018 were analyzed.Methods:From January 2011 to December 2018, 4 819 stool samples from children under 5 years old with diarrhea were collected monthly from 3 hospitals in Beijing. General information, clinical characteristics and other information of children were collected. RVA was detected by enzyme-linked immunosorbent assay (ELISA), genotype was identified by multiple semi-nested RT-PCR. The Vesikari clinical severity score was used to define the severity of diarrhea in children. Dichotomous unconditional logistic regression was used to analyze clinical symptoms and other differences between RVA positive and negative cases. Chi-square and Fisher direct probability tests were used to compare the composition among different groups.Results:A total of 4 819 fecal samples were collected, 953 were positive for RVA, the positive detection rate was 19.78%. The positive rate of RVA was high in the younger age group, and the incidence was high in winter and spring. RVA-positive children had more risk on diarrhea ≥5 times a day, vomiting symptoms, fever, mild dehydration, and Vesikari score ≥11. The positive rate of RVA in watery stool samples (26.13%, 214/819) and infectious diarrhea cases (42.20%, 265/628) was the highest respectively. There were no significant differences in clinical symptoms, clinical diagnoses and fecal traits among children with different RVA genotypes.Conclusions:The clinical symptoms of RVA diarrhea were severe in children. RVA genotype did not affect the clinical symptoms. Stool traits (watery stools) and Vesikari score can assist physicians in diagnosing RVA diarrhea.

COVID-19 ; China/epidemiology* ; Disease Outbreaks ; Humans ; SARS-CoV-2

Objective:To analyze the relationship between the cycle threshold ( Ct) values of N gene of COVID-19 cases and the secondary attack risk in close contacts, and identify the relationship between respiratory viral load and infectivity in COVID-19 cases. Methods:The COVID-19 cases with records of Ct values of N gene within 0-7 days of onset were selected, and their close contacts were recruited as the subjects of study. We collected the information of close contacts, including name, gender, age, isolation mode, exposure mode and outcome (whether they were infected with SARS-CoV-2 or not) and other variables. Multivariate logistic regression models were used to identify the relationship between Ct values of N gene of COVID-19 cases and secondary attack risk in close contacts. Results:A total of 1 618 close contacts were recruited, in whom 77 were confirmed as symptomatic or asymptomatic COVID-19 patients with overall secondary attack rate of 4.8%. The multivariate logistic regression analysis indicated that eating together ( OR=2.741, P=0.054), living together ( OR=9.721, P<0.001), non-centralized isolation ( OR=18.437, P<0.001) and COVID-19 case's values of N gene within 0-7 days of onset being <20 ( OR=8.998, P=0.004) or 20-25 ( OR=3.547, P=0.032) were significantly associated with higher likelihood of being infected with SARS-CoV-2 in close contacts. Conclusion:The results indicated that positive relationship exists between respiratory viral load and infectivity in COVID-19 cases, suggesting that Ct values of N gene can be used as an early warning indicator for the management of close contacts of COVID-19 cases.

Objective:To analyze epidemiological characteristics of influenza in Beijing during 2015—2020 influenza seasons.Methods:Weekly numbers of cases with influenza-like illness and weekly data of virologic surveillance was used to analyze epidemic trend and characteristics of influenza.Results:From June 26, 2015 to June 28, 2020, influenza-like illness (ILI) was 1.58%. A total of 49868 pharyngeal swab samples were collected from ILI cases, and positive rate of influenza virus nucleic acid was 16.32% by real-time PCR. Of these positive samples, 40.89% (6 474) were A(H3N2), 27.86% (4 410) were A (H3N2), 20.78% (3 290) were B/Victoria lineage, and 10.09%(1597) were B/Yamagata lineage. There were correlation between ILI and positive rate of influenza virus ( r=0.796, P<0.001), and ILI percentage and positive rate were also correlated ( r=0.808, P<0.001). The active duration in 2018—2018, 2018—2019 influenza seasons were longer. Weekly numbers of influenza-like illness cases of 2017—2018, 2018—2019 influenza seasons were higher (49 628 and 71 555), peak value of positive rate in the above seasons was higher (58.51% and 57.08%). Conclusions:The epidemic characteristics of influenza during 2015—2020 years was in accordance with the temperate regions of the northern hemisphere. There were longer active period and higher epidemic level in 2017—2018, 2018—2019 influenza seasons. The dominant influenza virus subtypes varied in the different seasons.

Objective To calculate both the epidemic and intensity thresholds for different levels in Beijing and to establish a tiered alert system in the 2018-2019 influenza season as well as to evaluate the performance of calculated thresholds.Method Weekly count of influenza-like illness and percentage of influenza-like illness (ILI％) of the last five influenza seasons were modeled by 'moving epidemic method'(MEM) to calculate the influenza epidemic and intensity thresholds at different levels.A cross-validation procedure was used to evaluate the performance.Indicators of Matthew correlation coefficient,Youden's index,sensitivity and specificity were calculated.Results For weekly count of influenza-like illness,data showed that the epidemic threshold for 2018-2019influenza season was 12 984 and the medium,high and very high intensity thresholds were 22 503,37 589,47 157,respectively.Matthew correlation coefficient of the epidemic threshold was 62％ and youden's index as 60％,sensitivity as 69％,specificity as 91％.Data on weekly ILI％,the epidemic threshold for 2018-2019 influenza season was 1.66％,with medium,high and very high intensity thresholds as 2.46％,3.84％ and 4.66％,respectively.The overall Matthew correlation coefficient of the epidemic threshold was 59％,with 54％ for the Youden's index,sensitivity as 60％ and specificity as 94％.Conclusions MEM produced a good specific signal for detecting the influenza epidemics and the accuracy of the method was acceptable.The early warning performance regarding the application of weekly count on influenza-like illness was slightly better than ILI％.This method could be applied in the practical influenza epidemic alert "work in Beijing".

Objective: The objective was to identify the incidence of influenza-like syndromes and related health behavior factors among Beijing residents. Methods: From December 6, 2013 to January 16, 2014, we selected 150 villages or communities from 30 towns or streets as survey locations using a multi-stage random sampling method, and then conducted a cross-sectional study among 7 354 residents who aged 18 years or above and had live in Beijing for more than a half year using self-administered anonymous questionnaires, and totally 7 327 valid questionnaires are collected. The questionnaire consisted of demographic information, self-reported influenza-like syndromes in the past two weeks, and health behaviors. Multiple logistic regression models were used to identify the factors associated with self-reported influenza-like syndromes. Results: The mean (SD) age of the partcipants was 44.6 (15.2) years. Among them, 6.9% (506 cases) reported having influenza like illness during the past two weeks. The multiple logistic regression analysis indicated that regular physical exercise, optimal hand hygiene, and avoidance of going to the crowded places during respiratory infectious disease epidemics were significantly associated with a lower likelihood of reporting influenza-like syndromes, compared with those without regular physical exercises, without optimal hand hygiene, and not avoiding going to the crowded places, and the OR(95%CI) were 0.80 (0.66-0.97), 0.75 (0.57-0.99) and 0.80 (0.65-0.98), respectively. Conclusion Personal health behaviors were associated with the incidence of respiratory infectious diseases such as influenza in Beijing, and future interventions to improve personal hygiene behaviors are needed to prevent the spread of respiratory infectious diseases.

Objective This study aimed to explore the incidence trends and onset features of scarlet fever during the years of epidemic,from 2006 to 2015,in Beijing.Methods Spatial,temporal and population distributions,prognosis of the reported cases and surveillance data on scarlet fever and other streptococcal infections (including the patients of streptococcal infection,tonsillitis and isthmitis) were analyzed by the descriptive epidemiological methods.Results A total of 27 987 scarlet fever cases were reported from 2006 to 2015,with the incidence rates as 7.04 to 18.53 per 100 000 persons during these years,except for 2011.A total of 6 152 cases were reported in 2011,with the incidence of 31.37 per 100 000 persons,significantly higher than the average levels of the other years.There were more cases reported in rural-urban continuum,in summer and winter,with most of the cases were children in primary schools and infant-institutes.From May to December in 2011,4 332 cases were interviewed three weeks after the disease onset,and their conditions improved or recovered,with no death or complication appeared at the follow-up period.There were 2 725 cases of scarlet fever and 104 013 clinical cases of streptococcal infections reported in 36 surveillance hospitals during the same period.The ratio between numbers of scarlet fever cases and streptococcal infection was 1 ∶ 38.17.The weekly numbers of scarlet fever were remarkably correlated to the streptococcal infections,with a Pearson's correlation coefficient as 0.729 (P＜0.001).Accordingly,we estimated that about 21.4 thousand clinical cases of streptococcal infections that were caused by Group A streptococcus in 2011,in Beijing.Conclusions Incidence of scarlet fever in 2011 was significantly higher than the average levels of other years in Beijing,but characteristics on spatial,temporal and population distributions of scarlet fever remained the same,with good prognosis of the reported cases.A large number of culture-positive Group A streptococcus infections among all the clinical cases of streptococcal infection might have been served as important source on septic infection,of scarlet fever.

Objective To investigate human exposure to live poultry (poultry feeding and purchasing) in the residents in Beijing and related factors during the second wave of avian influenza A (H7N9) epidemic during 2013-2014, and provide scientific evidence for avian influenza prevention and control. Methods A total of 7366 adults aged ≥18 years were selected through multi-stage stratified sampling in Beijing for a questionnaire survey. Logistic regression model was used to analyze the influence factors of human exposure to live poultry. Results The live poultry feeding rate and live poultry purchasing rate in residents in Beijing in the past year were 5.3%(95%CI:4.8%-5.8%) and 6.0% (95%CI: 5.5%-6.5%) respectively. Logistic regression analysis indicated that lower educational level of primary school and below, (OR=1.82, 95%CI:1.22-2.72);being farmer (OR=2.49, 95%CI:1.89-3.29) or being unemployed (OR=1.65, 95%CI:1.08-2.52);being non local resident (OR=1.54, 95%CI:1.10-2.16);living in suburban area (OR=2.36, 95%CI:1.77-3.16);having one child (OR=1.76, 95%CI: 1.42-2.17) or ≥2 children (OR=2.15, 95%CI: 1.43-3.22) in the family were the risk factors associated with feeding poultry compared with higher educational level of college and above, being employed, being local resident, living in urban area and having no child. And being farmer (OR=1.61, 95%CI:1.27-2.02);being non local resident (OR=1.76, 95%CI:1.31-2.35);living in suburban area (OR=2.05, 95%CI:1.61-2.61);having one child (OR=1.24, 95%CI:1.02-1.52) or ≥2 children (OR=1.78, 95%CI: 1.21-2.63) were the risk factors for purchasing live poultry. Conclusion Some residents living in Beijing still have exposure to live poultry, and targeted measures should be taken to reduce the exposure to poultry.