ABSTRACT
OBJECTIVES: To evaluate the impact of early implementation of public health and social measures (PHSMs) on contact rates over time and explore contact behavior of asymptomatic versus symptomatic cases. METHODS: We used the largest contact tracing data in China thus far to estimate the mean contacts over time by age groups and contact settings. We used bootstrap with replacement to quantify the uncertainty of contact matrixes. The Pearson correlation was performed to demonstrate the number of contacts over time in relation to the evolution of restrictions. In addition, we analyzed the index cases with a high number of contacts and index cases that produced a high number of secondary cases. RESULTS: Rapidly adapted PHSMs can reduce the mean contact rates in public places while increasing the mean contact rates within households. The mean contact rates were 11.81 (95% confidence interval, 11.61-12.01) for asymptomatic (at the time of investigation) cases and 6.70 (95% confidence interval, 6.54-6.87) for symptomatic cases. The percentage of asymptomatic cases (at the time of investigation) meeting >50 close contacts make up more than 65% of the overall cases. The percentage of asymptomatic cases producing >10 secondary cases account for more than 80% of the overall cases. CONCLUSION: PHSMs may increase the contacts within the household, necessitating the need for pertinent prevention strategies at home. Asymptomatic cases can contribute significantly to Omicron transmission. By making asymptomatic people aware that they are already contagious, hence limiting their social contacts, it is possible to lower the transmission risk.
Subject(s)
COVID-19 , SARS-CoV-2 , Humans , COVID-19/epidemiology , Public Health , Contact Tracing , Disease Outbreaks , China/epidemiologyABSTRACT
INTRODUCTION: The coronavirus disease 2019 (COVID-19) pandemic recently affected Taiwan, China. This study aimed to calculate the transmissibility of COVID-19 to predict trends and evaluate the effects of interventions. METHODS: The data of reported COVID-19 cases was collected from April 20 to May 26, 2021, which included daily reported data (Scenario I) and reported data after adjustment (Scenario II). A susceptible-exposed-symptomatic-asymptomatic-recovered model was developed to fit the data. The effective reproductive number (Reff ) was used to estimate the transmissibility of COVID-19. RESULTS: A total of 4,854 cases were collected for the modelling. In Scenario I, the intervention has already taken some effects from May 17 to May 26 (the Reff reduced to 2.1). When the Reff was set as 0.1, the epidemic was projected to end on July 4, and a total of 1,997 cases and 855 asymptomatic individuals would have been reported. In Scenario II, the interventions were projected as having been effective from May 24 to May 26 (the Reff reduced to 0.4). When the Reff was set as 0.1, the epidemic was projected to end on July 1, and a total of 1,482 cases and 635 asymptomatic individuals would have been reported. CONCLUSION: The epidemic of COVID-19 was projected to end after at least one month, even if the most effective interventions were applied in Taiwan, China. Although there were some positive effects of intervention in Taiwan, China.
ABSTRACT
Epidemiological characteristics of coronavirus diseases (COVID-19) were described and in FuJian to provide evidence for prevention and control. All COVID-19 cases from FuJian reported as of February 21, 2020 were extracted from Chinese Infectious Disease Detection Report Information system. Descriptive epidemiological methods were used to analyze the characteristics of cases, including examination of age distributions and sex ratios, time and geographical distributions, and the clustering features. Until February 21, 2020, a total of 298 patient: including records-293(98.3%) confirmed cases, 2(0.7%) suspected cases, and 3 asymptomatic cases (1.0%)-were analyzed. One deaths occurred among confirmed cases for a case fatality rate of 0.3%. The majority of confirmed cases were common pneumonia, with a total of 199 cases, accounting for 67.9%. Among confirmed cases, most were aged 25-54 years (67.9%), and the ratio of males to females is 1.22 to 1. In addition to PingTan, cases were found in all the other 9 cities, mainly in FuZhou (71 cases, 24.2%), PuTian (55 cases,18.8%) and QuanZhou (46 cases, 15.7%).By the statistics of county (city, district) distribution, 27 counties (city, district) have not reported confirmed cases. A total of 50 clusters involving 177 cases have been reported. Most cases in Fujian had a history of travel to or residence in other provinces, and the imported cases are mainly young and middle-aged, while the local cases are mainly middle-aged and elderly. Confirmed cases haved been reported in all cities except Pingtan. The prevalence curve of imported cases was consistent with that of people returning to Fujian, and the prevalence of local cases was one week later than that of imported cases. Clusters, mainly family clusters had been reported in all cities.