Showing papers in "Chinese journal of epidemiology in 2020"

The epidemiological characteristics of an outbreak of 2019 novel coronavirus diseases (COVID-19) in China

Abstract: Objective An outbreak of 2019 novel coronavirus diseases (COVID-19) in Wuhan, China has spread quickly nationwide. Here, we report results of a descriptive, exploratory analysis of all cases diagnosed as of February 11, 2020. Methods All COVID-19 cases reported through February 11, 2020 were extracted from China’s Infectious Disease Information System. Analyses included: 1) summary of patient characteristics; 2) examination of age distributions and sex ratios; 3) calculation of case fatality and mortality rates; 4) geo-temporal analysis of viral spread; 5) epidemiological curve construction; and 6) subgroup analysis. Results A total of 72 314 patient records-44 672 (61.8%) confirmed cases, 16 186 (22.4%) suspected cases, 10567 (14.6%) clinical diagnosed cases (Hubei only), and 889 asymptomatic cases (1.2%)-contributed data for the analysis. Among confirmed cases, most were aged 30-79 years (86.6%), diagnosed in Hubei (74.7%), and considered mild/mild pneumonia (80.9%). A total of 1 023 deaths occurred among confirmed cases for an overall case-fatality rate of 2.3%. The COVID-19 spread outward from Hubei sometime after December 2019 and by February 11, 2020, 1 386 counties across all 31 provinces were affected. The epidemic curve of onset of symptoms peaked in January 23-26, then began to decline leading up to February 11. A total of 1 716 health workers have become infected and 5 have died (0.3%). Conclusions The COVID-19 epidemic has spread very quickly. It only took 30 days to expand from Hubei to the rest of Mainland China. With many people returning from a long holiday, China needs to prepare for the possible rebound of the epidemic. Key words: 2019 Novel Coronavirus; Outbreak; Epidemiological characteristics

[Epidemiological characteristics of infection in COVID-19 close contacts in Ningbo city].

Abstract: Objective: To estimate the infection rate of close contacts of COVID-19 cases, and to evaluate the risk of COVID-19 under different exposure conditions. Methods: A prospective study was used to conduct continuous quarantine medical observations of close contacts of people infected with COVID-19, collect epidemiological, clinical manifestations, and laboratory test data to estimate the infection rate of close contacts under different exposures. Results: The epidemiological curve of COVID-19 in Ningbo showed persistent human-to-human characteristics. A total of 2 147 close contacts were tracked and investigated. The total infection rate was 6.15%. The infection rates of confirmed cases and positive contacts were 6.30% and 4.11%, respectively. The difference was not statistically significant (P>0.05). Among close contacts of different relationships, friends/pilgrims (22.31%), family members (18.01%), and relatives (4.73%) have a higher infection rate, and close contacts of medical staff were not infected. Differences in infection rates among the close contacts were statistically significant (P<0.005). Living with the case (13.26%), taking the same transportation (11.91%), and dining together (7.18%) are high risk factors for infection. Cross-infection in the hospital should not be ignored (1.94%). The median of incubation period is 5 days. Conclusion: The infection rate of close contacts of COVID-19 cases is high, and isolation medical observation measures should be implemented in strict accordance with the close contact management plan.

[Epidemiological characteristics of confirmed COVID-19 cases in Tianjin].

Abstract: Objective: To investigate the clinical and epidemiological characteristics of 135 confirmed cases of COVID-19 in Tianjin. Methods: The clinical and epidemiological data of 135 cases of COVID-19 in Tianjin were collected, and the data were analyzed with descriptive method. The factors influencing the severity of the illness were analyzed. Results: Among the 135 COVID-19 cases, 72 were males and 63 were females, the age of the cases was (48.62±16.83) years, and the case fatality rate was 2.22%. Local transmission caused 74.81% of the cases. A total of 33 clusters occurred, involving 85.92% of all COVID-19 cases. The median of the incubation period of COVID-19 was 6.50 days, the average generation interval was 5 days, and the household secondary transmission rate was 20.46%. Fever was the main symptom (78.63%), followed by cough (56.48%). Multivariate regression analysis indicated that age (OR=1.038, 95%CI: 1.010-1.167) and the number of chronic underlying diseases (OR=1.709, 95%CI: 1.052-2.777) were the risk factors of severe illness. Conclusions: Fever was the main symptom at the early phase of COVID-19 in Tianjin, and the local cluster cases accounted for high proportion in confirmed COVID-19 cases reported in Tianjin. Severe illness was prone to occur in people with old age and multi underlying diseases. Strict isolation of close contacts and intensive care of high-risk groups are the main measures to reduce the morbidity and case fatality of COVID-19.

[Quick community survey on the impact of COVID-19 outbreak for the healthcare of people living with HIV].

Abstract: Objective: To collect the current status and healthcare needs of people living with HIV (PLHIV) in China during the COVID-19 outbreak to inform quick response from government and communities. Methods: During February 5(th) to 10(th), 2020, a national anonymous survey was conducted using an online questionnaire among PLHIV at least 18 years of age and had started antiretroviral treatment (ART) to collect the information on COVID-19 prevention, HIV-related health services and the needs on psychosocial support. Current status and needs of people living with HIV were analyzed in Hubei and other regions. Results: A total of 1 014 valid questionnaires were collected, with PLHIV respondents cross the country. The survey revealed that 93.79% of the respondents could obtain information regarding the prevention of COVID-19 from their communities or villages. Respondents were concerned with HIV-specific protective measures and personal protective equipment shortage. 32.64% of all respondents were not carrying sufficient antiretroviral medicines (ARVs) to meet the needs under traffic and travel restrictions, and some could face stock-outs in the coming month. In Hubei province where 53 respondents needed ARV refill, 64.15% reported difficulty accessing ARV due to the "blockage" . 28.93% respondents were in need of sociopsychological support, and 85.31% anticipated further improvement of the out-of-town ARV refill process from the government. Conclusion: PLHIV wants to know HIV-specific protective measures against COVID-19 outbreak. PLHIV who returned to their home-towns and affected by the lock-downs reported challenges with refills. We should undertake a more systematic study on impacts of the COVID-19 on PLHIV to develop preparedness capacity for future public health emergency.

[Investigation and analysis on characteristics of a cluster of COVID-19 associated with exposure in a department store in Tianjin].

Abstract: Objective: To describe the epidemiological characteristics of a cluster of COVID-19 cases reported in Baodi district of Tianjin as of 18 February, 2020, which might be associated with the exposure in a local department store, and provide suggestions for prevention and control strategy development. Methods: The basic characteristics, time and area distributions, clinical manifestations, epidemiological history and transmission mode of the COVID-19 cases associated with the department store exposure were analyzed. Results: A total of 40 COVID-19 cases were associated with the department store exposure, accounting for 75.47% of the total confirmed cases (53 cases) reported in Baodi district. The cases were mainly at the age of 60 years or older (35.00%) and farmers (40.00%). The main clinical manifestations included fever (95.00%), cough (35.00%), and diarrhea (15.00%). The proportion of confirmed severe cases was 32.50%. The incidence curve showed that the incidence peak occurred on 31 January, 2020. Among the 40 cases, 6(15.00%) were department store employees, 19 (47.50%) were customers and 15 (37.50%) were close contacts (secondary cases). The first case occurred on 21 January, 2020, this case was a department store employee who had a purchasing history at whole sale markets in other provinces and cities before the onset, and 3 employees were still on duty after symptom onsets. The median of the incubation period of customer cases was 6 days, and the median of the interval between onset and medical treatment of customer cases was 7 days. Conclusion: This was a cluster epidemic of COVID-19, which might be associated with the exposure in the department store. By now, the current prevention and control measures have achieved satisfied effects.

[Estimating the basic reproduction number of COVID-19 in Wuhan, China].

Abstract: Objective: The number of confirmed and suspected cases of the COVID-19 in Hubei province is still increasing. However, the estimations of the basic reproduction number of COVID-19 varied greatly across studies. The objectives of this study are 1) to estimate the basic reproduction number (R(0)) of COVID-19 reflecting the infectiousness of the virus and 2) to assess the effectiveness of a range of controlling intervention. Methods: The reported number of daily confirmed cases from January 17 to February 8, 2020 in Hubei province were collected and used for model fit. Four methods, the exponential growth (EG), maximum likelihood estimation (ML), sequential Bayesian method (SB) and time dependent reproduction numbers (TD), were applied to estimate the R(0). Results: Among the four methods, the EG method fitted the data best. The estimated R(0) was 3.49 (95%CI: 3.42-3.58) by using EG method. The R(0) was estimated to be 2.95 (95%CI: 2.86-3.03) after taking control measures. Conclusions: In the early stage of the epidemic, it is appropriate to estimate R(0) using the EG method. Meanwhile, timely and effective control measures were warranted to further reduce the spread of COVID-19.

Fitting and forecasting the trend of COVID-19 by SEIR + CAQ dynamic model

Abstract: Objectives: Fitting and forecasting the trend of COVID-19 epidemics. Methods: Based on SEIR dynamic model, considering the COVID-19 transmission mechanism, infection spectrum and prevention and control procedures, we developed SEIR(+CAQ) dynamic model to fit the frequencies of laboratory confirmed cases obtained from the government official websites. The data from January 20, 2020 to February 7, 2020 were used to fit the model, while the left data between February 8-12 were used to evaluate the quality of forecasting. Results: According to the cumulative number of confirmed cases between January 29 to February 7, the fitting bias of SEIR(+CAQ) model for overall China (except for cases of Hubei province), Hubei province (except for cases of Wuhan city) and Wuhan city was less than 5%. For the data of subsequent 5 days between February 8 to 12, which were not included in the model fitting, the prediction biases were less than 10%. Regardless of the cases diagnosed by clinical examines, the numbers of daily emerging cases of China (Hubei province not included), Hubei Province (Wuhan city not included) and Wuhan city reached the peak in the early February. Under the current strength of prevention and control, the total number of laboratory-confirmed cases in overall China will reach 80 417 till February 29, 2020, respectively. Conclusions: The proposed SEIR(+CAQ) dynamic model fits and forecasts the trend of novel coronavirus pneumonia well and provides evidence for decision making.

[Advances on presymptomatic or asymptomatic carrier transmission of COVID-19].

Abstract: COVID-19 is rapidly spreading. Patients in incubation period and healthy carriers are possible sources for transmission. However, such sources of infection cannot be effectively identified due to the symptoms absent. The research evidence is very lacking so far, although there are a few studies suggesting that presymptomatic or asymptomatic carrier may cause COVID-19 transmission. Nearly half of the literature is in the state of preprint without peer review. The question of "the degree to which presymptomatic or asymptomatic infections can transmit" is not fully understood. There is an urgent need to screen infected carriers in larger close contacts or in the general population, and assess their risk for transmission.

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

Abstract: 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.

[Contribution of asymptomatic and pre-symptomatic cases of COVID-19 in spreading virus and targeted control strategies].

Abstract: The asymptomatic carrier state of COVID-19 has become a topic of concern for preventing the rebound of possible epidemic. This review describes and defines the COVID-19 asymptomatic carrier state and outlines the methods for identifying, counting and reporting of these cases. The author elaborates that the asymptomatic carrier state can be further divided into asymptomatic infection and pre-symptomatic infection after extended follow-up based on the nature of the disease progression. The author presents the limited available data about the infectivity of asymptomatic and pre-symptomatic cases and their possible contributions to the overall epidemic of COVID-19 observed so far in China. Challenges of a possible second epidemic wave of COVID-19 caused by asymptomatic and pre-symptomatic cases are discussed and suggestions for control strategies and scientific research are provided.

[WITHDRAWN: Potential false-positive rate among the 'asymptomatic infected individuals' in close contacts of COVID-19 patients].

Abstract: Editor office’s response for Ahead of Print article withdrawn The article “Potential false-positive rate among the ‘asymptomatic infected individuals’ in close contacts of COVID-19 patients” was under strong discussion after pre-published. Questions from the readers mainly focused on the article’s results and conclusions were depended on theoretical deduction, but not the field epidemiology data and further researches were needed to prove the current theory. Based on previous discussions, the article was decided to be offline by the editorial board from the pre-publish lists. Objective: As the prevention and control of COVID-19continues to advance, the active nucleic acid test screening in the close contacts of the patients has been carrying out in many parts of China. However, the false-positive rate of positive results in the screening has not been reported up to now. But to clearify the false-positive rate during screening is important in COVID-19 control and prevention. Methods: Point values and reasonable ranges of the indicators which impact the false-positive rate of positive results were estimated based on the information available to us at present. The false-positive rate of positive results in the active screening was deduced, and univariate and multivariate-probabilistic sensitivity analyses were performed to understand the robustness of the findings. Results: When the infection rate of the close contacts and the sensitivity and specificity of reported results were taken as the point estimates, the positive predictive value of the active screening was only 19.67%, in contrast, the false-positive rate of positive results was 80.33%. The multivariate-probabilistic sensitivity analysis results supported the base-case findings, with a 75% probability for the false-positive rate of positive results over 47%. Conclusions: In the close contacts of COVID-19 patients, nearly half or even more of the 'asymptomatic infected individuals' reported in the active nucleic acid test screening might be false positives.

[Study on assessing early epidemiological parameters of COVID-19 epidemic in China].

Abstract: Objective: To study the early dynamics of the epidemic of coronavirus disease (COVID-19) in China from 15 to 31 January, 2020, and estimate the corresponding epidemiological parameters (incubation period, generation interval and basic reproduction number) of the epidemic. Methods: By means of Weibull, Gamma and Lognormal distributions methods, we estimated the probability distribution of the incubation period and generation interval data obtained from the reported COVID-19 cases. Moreover, the AIC criterion was used to determine the optimal distribution. Considering the epidemic is ongoing, the exponential growth model was used to fit the incidence data of COVID-19 from 10 to 31 January, 2020, and exponential growth method, maximum likelihood method and SEIR model were used to estimate the basic reproduction number. Results: Early COVID-19 cases kept an increase in exponential growth manner before 26 January, 2020, then the increase trend became slower. The average incubation period was 5.01 (95%CI: 4.31-5.69) days; the average generation interval was 6.03 (95%CI: 5.20-6.91) days. The basic reproduction number was estimated to be 3.74 (95%CI: 3.63-3.87), 3.16 (95%CI: 2.90-3.43), and 3.91 (95%CI: 3.71-4.11) by three methods, respectively. Conclusions: The Gamma distribution fits both the generation interval and incubation period best, and the mean value of generation interval is 1.02 day longer than that of incubation period. The relatively high basic reproduction number indicates that the epidemic is still serious; Based on our analysis, the turning point of the epidemic would be seen on 26 January, the growth rate would be lower afterwards.

[The preliminary analysis on the characteristics of the cluster for the COVID-19].

Abstract: Since December 2019, COVID-19, a new emerging infection disease, has spread in 27 countries and regions. The clusters of many cases were reported with the epidemic progresses. We collected currently available information for 377 COVID-19 clusters (1 719 cases), excluded the hospital clusters and Hubei cases, during the period from January 1 to February 20, 2020. There were 297 family clusters (79%), case median was 4; 39 clusters of dining (10%), case median was 5; 23 clusters of shopping malls or supermarkets (6%), case median was 13; 12 clusters of work units (3%), case median was 6, and 6 clusters of transportation. We selected 325 cases to estimate the incubation period and its range was 1 to 20 days, median was 7 days, and mode was 4 days. The analysis of the epidemic situation in a department store in China indicated that there was a possibility of patients as the source of infection during the incubation period of the epidemic. From February 5 to 21, 2020, 634 persons were infected on the Diamond Princess Liner. All persons are susceptible to the 2019 coronavirus. Age, patients during the incubation period and the worse environment might be the cause of the cases rising. The progress of the two typical outbreaks clearly demonstrated the spread of the early cases in Wuhan. In conclusion, screening and isolating close contacts remained essential other than clinical treatment during the epidemic. Especially for the healthy people in the epidemic area, isolation was the key.

[Epidemiological investigation of a family clustering of COVID-19].

Abstract: Objective: To investigate the epidemiological characteristics of a family clustering of COVID-19. Methods: Field epidemiological survey was conducted. Results: Case 1 of the long-term residents from Hubei province was the source of infection of this family clustering. There were 6 cases (from case 2 to case 7) infected in the whole incubation period. The incubation period was more than 14 days for 3 of the second-generation cases. Routes of transmission included respiratory droplets (from case 1 transmitted to case 6, from case 1 to her family members) and close contact (from case 1 to other cases in her family). All the age groups were generally susceptible, while elderly were easier to progress to critically ill. Besides respiratory symptoms, there were also gastrointestinal symptoms, of which diarrhea was the most common one. Conclusions: Family clustering had been an important part for COVID-19 cases.

[Epidemiological analysis on a family cluster of COVID-19].

Abstract: Objective: To understand the possible transmission route of a family cluster of COVID-19 in Zhengzhou and the potential infectivity of COVID-19 in incubation period, and provide scientific evidence for the timely control of infectious source and curb the spread of the epidemic. Methods: Epidemiological investigation was conducted for a family cluster of COVID-19 (8 cases) with descriptive epidemiological method, and respiratory tract samples of the cases were collected for the nucleic acid detection of virus by RT-PCR. Results: Two primary cases, which occurred on 31 January and 1 February, 2020, respectively, had a common exposure history in Wuhan. The other six family members had onsets on 30 January, 31 January, 1 February (three cases) and 3 February, 2020. Conclusions: In this family cluster of COVID-19, six family members were infected through common family exposure to the 2 primary cases. Five secondary cases had onsets earlier than or on the same day as the primary cases, indicating that COVID-19 is contagious in incubation period, and the home isolation in the early phase of the epidemic might lead to the risk of family cluster of COVID-19.

[COVID-19 pandemic: global epidemiological trends and China's subsequent preparedness and responses].

Abstract: The outbreak of COVID-19 has spread quickly across 114 countries/territories/areas in six continents worldwide and has been announced as a pandemic by WHO. This study analyzed global COVID-19 epidemiological trends, examined impact of the pandemic on global health security, diplomacy, and social environment in China, and provided short- and long-term strategic policy recommendations for China's subsequent preparedness and responses.

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

Abstract: 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.

Urgent research agenda for the novel coronavirus epidemic: transmission and non-pharmaceutical mitigation strategies

Abstract: Coronavirus disease 2019 (COVID-19) is an ongoing global pandemic with very limited specific treatments To fight COVID-19, various traditional antiviral medicines havebeen prescribed in China to infected patients with mild to moderate symptoms and received unexpected success in controlling the disease However, the molecular mechanisms of how these herbal medicines interact with the virus have remained elusive It is well known that the main protease (Mpro) of SARS-CoV-2 plays an important role in maturation of many viral proteins such as the RNA-dependent RNA polymerase Here,we explore the underlying molecular mechanisms of the computationally determined tocandidate–rutin, a key component in many traditional antiviral medicines such as Lianhuaqinwen and Shuanghuanlian, for inhibiting the viral target–Mpro Using in silico methods (docking and molecular dynamics simulations), we revealed the dynamics and energetics of rutin when interacting with the Mpro of SARS-CoV-2, suggesting that the highly hydrophilic rutin molecule can be bound inside the Mpro’ pocket (active site) and possibly inhibit its biological functions In addition, we optimized the structure of rutin and designed a more hydrophobic analog which satisfies the rule of five for western medicines and demonstrated that it possesses a much stronger binding affinity to the SARS-COV-2’s Mpro br /div

[Clinical outcomes of COVID-19 cases and influencing factors in Guangdong province].

Abstract: 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 1 049 (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 12(th) day after onset (P(25), P(75): 9(th) to 15(th) 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 (aHR=1.87, 95%CI: 1.43-2.46), older age (aHR=1.67, 95%CI: 1.51-1.85), seeking medical care on day 2-3 after onset (aHR=1.73, 95%CI: 1.20-2.50) pre-existing diabetes (aHR=1.75, 95%CI: 1.12-2.73) and hypertension (aHR=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.

[Prediction modeling with data fusion and prevention strategy analysis for the COVID-19 outbreak].

Abstract: Since December 2019, the outbreak of COVID-19 in Wuhan has spread rapidly due to population movement during the Spring Festival holidays. Since January 23rd, 2020, the strategies of containment and contact tracing followed by quarantine and isolation has been implemented extensively in mainland China, and the rates of detection and confirmation have been continuously increased, which have effectively suppressed the rapid spread of the epidemic. In the early stage of the outbreak of COVID-19, it is of great practical significance to analyze the transmission risk of the epidemic and evaluate the effectiveness and timeliness of prevention and control strategies by using mathematical models and combining with a small amount of real-time updated multi-source data. On the basis of our previous research, we systematically introduce how to establish the transmission dynamic models in line with current Chinese prevention and control strategies step by step, according to the different epidemic stages and the improvement of the data. By summarized our modelling and assessing ideas, the model formulations vary from autonomous to non-autonomous dynamic systems, the risk assessment index changes from the basic regeneration number to the effective regeneration number, and the epidemic development and assessment evolve from the early SEIHR transmission model-based dynamics to the recent dynamics which are mainly associated with the variation of the isolated and suspected population sizes.

[Dynamic basic reproduction number based evaluation for current prevention and control of COVID-19 outbreak in China].

Abstract: Objective: To evaluate the current status of the prevention and control of coronavirus disease (COVID-19) outbreak in China, establish a predictive model to evaluate the effects of the current prevention and control strategies, and provide scientific information for decision-making departments. Methods: Based on the epidemic data of COVID-19 openly accessed from national health authorities, we estimated the dynamic basic reproduction number R(0)(t) to evaluate the effects of the current COVID-19 prevention and control strategies in all the provinces (municipalities and autonomous regions) as well as in Wuhan and the changes in infectivity of COVID-19 over time. Results: For the stability of the results, 24 provinces (municipality) with more than 100 confirmed COVID-19 cases were included in the analysis. At the beginning of the outbreak, the R(0)(t) showed unstable trend with big variances. As the strengthening of the prevention and control strategies, R(0)(t) began to show a downward trend in late January, and became stable in February. By the time of data analysis, 18 provinces (municipality) (75%) had the R(0)(t)s less than 1. The results could be used for the decision making to free population floating conditionally. Conclusions: Dynamic R(0)(t) is useful in the evaluation of the change in infectivity of COVID-19, the prevention and control strategies for the COVID-19 outbreak have shown preliminary effects, if continues, it is expected to control the COVID-19 outbreak in China in near future.

[Advances on the asymptomatic infection of COVID-19].

Abstract: The COVID-19 outbreak in China has been gradually controlled. At present, the management and risk assessment of asymptomatic infected cases has become an urgent problem to be addressed. Asymptomatic case is mainly detected by close contact screening, cluster epidemic investigation, infection source tracking investigation, and active detection of target population. Currently, research on the spread risk from asymptomatic cases was limited, and lacking the data relates to the distribution of asymptomatic cases in large community population. Pathogen detection using PCR is suitable for screening in close contacts of confirmed cases and should be started as early as possible. The antibody test is more suitable for screening in general population where the source of infection is unclear. The management of asymptomatic cases now in China focuses on isolation and medical observation according to the guideline of "early detection, early report, early isolation and early treatment" .

[Epidemiological analysis on 1 052 cases of COVID-19 in epidemic clusters].

Abstract: Objective: To understand the epidemiological characteristics of the cases of COVID-19 epidemic clusters, and explore the influence of family factors and social factors such as group activities on the spread of the disease. Methods: The data of cases of COVID-19 epidemic clusters from 19 January, 2020 to 25 February, 2020 were collected from the official platforms of 36 cities in 6 provinces in China. Descriptive statistical methods, χ(2) test and curve fitting were used to analyze the epidemiological characteristics of the clustered cases. Results: By 25 February, 2020, the data of 1 052 cases in 366 epidemic clusters were collected. In these clustered cases, 86.9%(914/1 050) occurred in families. Among the 1 046 cases with gender information, 513 were males (49.0%) and 533 were females (51.0%). The cases were mainly young adults between 18 and 59 years old, accounting for 68.5% (711/1 038). In the 366 epidemic clusters , the clusters in which the first confirmed cases with the history of sojourn in Wuhan or Hubei accounted for 47.0%(172/366). From 19 January to 3 February, 2020, the first confirmed cases with Wuhan or Hubei sojourn history accounted for 66.5%. From 4 to 25 February, the first confirmed cases who had Wuhan or Hubei sojourn history accounted for only 18.2%. The median of interval between the first generation case onset and the second generation case onset was 5 (2-8) days. The median of onset- diagnosis interval of the initial cases was 6 (3-9) days, and the median of onset-diagnosis interval of the secondary cases was 5 (3-8) days. Conclusions: Epidemic clusters of COVID-19 were common in many cities outside Wuhan and Hubei. Close contact in family was one of the main causes for the spread of household transmission of the virus. After 4 February, the epidemic clusters were mainly caused by the first generation or second generation cases in local areas, and the time for diagnosis became shorter.

Changing trends in the levels of blood pressure and prevalence of hypertension among Chinese children and adolescents from 1991 to 2015

Abstract: Objective: To examine the trends in blood pressure levels and prevalence of hypertension among Chinese children and adolescents aged 7-17 years from 1991 to 2015, using the four blood pressure references for children and adolescents, in order to provide basic data for the prevention and control of hypertension. Methods: A total of 14 622 children and adolescents aged 7-17 years were selected from the China Health and Nutrition Survey 1991-2015. Hypertension was defined under the four latest published references including the 2018 Health Industry pediatric blood pressure reference (Industry Reference), the 2018 Chinese Hypertension Prevention and Treatment Guideline reference (Guideline Reference), the 2016 International Child Blood Pressure Reference (International Reference), and the 2017 Blood Pressure Reference by the American Academy of Pediatrics (US Reference). Multivariable liner regression model was used to examine the trends in blood pressure levels from 1991 to 2015, and multivariable logistic regression model was used to examine the trend in prevalence of hypertension from 1991 to 2015. Results: After adjusted for factors as age, sex, region, and BMI, the SBP appeared an increase, from 96.1 mmHg in 1991 to 102.7 mmHg and DBP from 62.6 mmHg to 67.4 mmHg (all P for trend <0.001) in 2015. The prevalence rates of hypertension defined by Industry Reference, Guideline Reference, International Reference and US Reference increased from 5.7%, 8.9%, 4.4% and 8.1% in 1991, to 12.8%, 20.5%, 13.1% and 17.8% (all P for trend <0.001) in 2015, respectively. Conclusion: Both levels of blood pressure and the prevalence of hypertension increased significantly in Chinese children and adolescents from 1991 to 2015.

[Inference of start time of resurgent COVID-19 epidemic in Beijing with SEIR dynamics model and evaluation of control measure effect].

Abstract: Objective: To infer the start time of the resurgent COVID-19 epidemic in Xinfadi wholesale market in Beijing in June 2020 and evaluate the effect of comprehensive prevention and control measures in this epidemic. Methods: SEIR dynamics model was used to fit daily onset infections to search the start date of this resurgent COVID-19 epidemic in Beijing. The number of cumulative infections from June 12 to July 1 in Beijing were fitted considering different levels of control strength. Results: The current reemerged COVID-19 epidemic in Beijing probably started between May 22 and May 28 (cumulative probability: 95%), with the highest probability on May 25 (23%). The R(0) of the current reemerged COVID-19 epidemic was 4.22 (95%CI: 2.88-7.02). Dynamic model fitting suggested that by June 11, the cumulative number of COVID-19 cases would reached 99 (95%CI: 77-121), which was in line with the actual situation, and without control, by July 1, the cumulative number of COVID-19 cases would reach 65 090 (95%CI: 39 068-105 037). Since June 12, comprehensive prevention and control measures have been implemented in Beijing, as of July 1, compared with uncontrolled situation, the number of infections had been reduced by 99%, similar to the fitting result of a 95% reduction of the transmission rate. The sensitivity analysis showed consistent results. Conclusions: For the emergent outbreak of COVID-19, the dynamics model can be used to infer the start time of the transmission and help tracing the source of epidemic. The comprehensive prevention and control measures taken in Beijing have quickly blocked over 95% of the transmission routes and reduced 99% of the infections, containing the sudden epidemic timely and effectively, which have value in guiding the prevention and control of the epidemic in the future.

[Disease burden of colorectal cancer in China: any changes in recent years?]

Abstract: Objective: To update the disease burden of colorectal cancer (CRC) in Chinese population by integrating the latest multi-source evidences. Methods: Groups of data from GLOBOCAN, series of Chinese Cancer Registry Annual Report (annual report), Cancer Incidence in Five Continents (CI5), Global Burden of Disease Project 2017 (GBD), China Death Cause Surveillance Datasets and China Health Statistical Yearbooks (yearbook) were used to extract the information. Data on incidence, mortality, disability-adjusted life year (DALY) and percentage distribution of sub-location of CRC were used to analyze the latest disease burden in China, and age-standardized rates by world standard population were mainly used. Joinpoint Trend Analysis Software 4.7.0.0 was applied for time trend analysis. Data related to the economic burden of CRC in China were gathered by literature review. Results: (1) Current status: according to the latest annual report, the incidence and mortality rates of CRC were 17.1 per 100 000 and 7.9 per 100 000, respectively among the covered registration sites in 2015. The incidence ratios of male to female and that of urban to rural were 1.5 and 1.4, with the mortality ratios were 1.6 and 1.4, respectively. Similar to data from the annual report, the mortality rate was reported as 6.9 per 100 000 in 2017 by the surveillance data sets. Data from the GBD project showed that, the DALYs caused by CRC in China in 2017 was 4.254 million person years (doubled compared with that of 1990), accounting for 22.4% of the global burden of CRC. (2) Time trends: according to the annual reports, from 2009 to 2015, the incidence rate and mortality rate of CRC in China decreased by 10.2% and 9.5%, respectively. The same trend was also observed in urban sites, but was opposite in rural areas (increased 20.0% in incidence and 15.2% in mortality). Results from the Joinpoint analysis showed that the averaged annual percentage change (AAPC) was estimated as -1.6% (P 52%) than that in the rural areas (<44%). The CI5 Ⅺ data showed that ascending and sigmoid colons were more commonly seen among all the colon cancers. (4) Economic burden: the average annual growth rate of the medical expenditure per CRC patient in China ranged from 6.9% to 9.2%, and the 1-year out-of-pocket expenditure of a newly diagnosed patient accounted for about 60% of their previous-year household income. Conclusions: In China, the overall disease burden of CRC might have been decreased slightly but generally remained stable in the last several years, however, the rising burden appeared in the rural areas should not be ignored. In consistent with findings from a previous review, men and people from the urban areas are considered the target populations for CRC. The finding of higher proportion of colon cancer in urban areas suggests the impact of development of socioeconomic and medical technologies on CRC development and detection. The economic burden of CRC continued to grow.

[Analysis on cluster cases of COVID-19 in Tianjin].

Abstract: Objective: To understand the characteristics of clusters of COVID-19 cases in Tianjin, and provide epidemiological evidence for the prevention and control of COVID-19. Methods: The data of all the COVID-19 cluster cases in Tianjin, reported by 22 February 2020, were collected to analyze the characteristics of different types of the clusters. Results: A total of 115 COVID-19 cases were reported in 33 clusters in Tianjin included 28 family clusters (71 cases), 1 work place cluster (10 cases), 3 transport vehicle clusters (8 cases) and 1 public place cluster (26 cases). Family clusters were caused by the cases from the working place or public place clusters. Numbers of secondary cases of family clusters was between 1 to 7, the median number was 2. The interval from onset to diagnosis for the first case was longer than those of other cases in the familial clusters (Z=-2.406, P=0.016). The median of incubation period of the public place clusters was 2 days. The intervals from onset to diagnosis were significant different among the family, working place and public place clusters (H=8.843, P=0.012), and also significant differences in onset time among the secondary cases (H=16.607, P=0.000). Conclusions: In the surveillance of COVID-19 epidemic, special attention should be paid to places where clustering are prone to occur, and the epidemiological investigation should be carried out timely to confirm the cluster. To prevent the transmission of COVID-19, the close contacts of the patients should be transferred to an assigned observation place on time for single room isolation. The awareness of COVID-19 prevention is low in some rural areas, reflected by many mass gathering activities and delayed medical care seeking after onset. It is necessary to strengthen the health education and take control measures in early period of epidemic.

[Epidemiological characteristics of COVID-19 in Shaanxi province].

Abstract: Objective: To understand the epidemiological characteristics of COVID-19 cases in different epidemic stages in Gansu province. Methods: Epidemiological investigation was conducted to collect the information of confirmed COVID-19 cases, including demographic, epidemiological and clinical information. Results: As of 25 February 2020, a total of 91 confirmed COVID-19 cases had been reported in Gansu. The epidemic of COVID-19 in Gansu can be divided as three different stages, i.e. imported case stage, imported-case plus indigenous case stage, and indigenous case stage. A total of 63 cases were clustered cases (69.23%), 3 cases were medical staff infected with non-occupational exposure. The initial symptoms included fever (54.95%, 50/91), cough (52.75%, 48/91), or fatigue (28.57%, 26/91), the proportion of each symptom showed a decreasing trend along with the three epidemic stages, but only the differences in proportions of fever (trend χ2=2.20, P<0.05) and fatigue (trend χ2=3.18, P<0.05) among the three epidemic stages were statistically significant. The cases with critical severe symptoms accounted for 42.85% (6/14), 23.73% (14/59) and 16.67% (3/18), respectively, in three epidemic stages, showed a decreasing trend (H=6.45, P<0.05). Also, the incubation period prolonged along with the epidemic stage (F=51.65, P<0.01), but the intervals between disease onset and hospital visit (F=5.32, P<0.01), disease onset and diagnosis (F=5.25, P<0.01) became shorter along with the epidemic stage. Additionally, the basic reproduction number (R0) had decreased from 2.61 in imported case stage to 0.66 in indigenous case stage. Conclusions: The COVID-19 epidemic in Gansu was caused by the imported cases, and about 2/3 cases were clustered ones. No medical worker was observed to be infected by occupational exposure. With the progression of COVID-19 epidemic in Gansu, the change in initial symptom and incubation period suggests, the early screening cannot only depend on body temperature monitoring.

[Estimating the distribution of COVID-19 incubation period by interval-censored data estimation method].

Abstract: Objectives: The COVID-19 has been the public health issues of global concern, but the incubation period was still under discussion. This study aimed to estimate the incubation period distribution of COVID-19. Methods: The exposure and onset information of COVID-19 cases were collected from the official information platform of provincial or municipal health commissions. The distribution of COVID-19 incubation period was estimated based on the Log- normal, Gamma and Weibull distribution by interval-censored data estimation method. Results: A total of 109 confirmed cases were collected, with an average age of 39.825 years. The median COVID-19 incubation period based on Log-normal, Gamma, and Weibull distribution were 4.958 (P(25)-P(75): 3.472-7.318) days, 5.083 (P(25)-P(75): 3.511-7.314) days, and 5.695 (P(25)-P(75): 3.675-7.674) days, respectively. Gamma distribution had the largest log-likelihood result. Conclusions: The distribution of COVID-19 incubation period followed the Gamma distribution, and the interval-censored data estimation method can be used to estimate the incubation period distribution.