ABSTRACT
Objective: To analyze the epidemiological characteristics of a local COVID-19 outbreak in Qinzhou, Guangxi Zhuang autonomous region, and provide reference for the prevention and control of COVID-19 in the future. Methods The epidemiological and clinical information, analysis reports and laboratory test results of the COVID-19 cases were collected for a descriptive epidemiological analysis. Results A total of 97 COVID-19 cases, including 79 asymptomatic cases and 18 confirmed cases, were reported in Qinzhou during 12-24 March, 2022. Forty nine cases were males and 48 cases were females. The median of age of the cases was 32 (17.0, 44.5) years. The median of incubation period was 3 days. The median of latent period was 2 days. A total of 3841 close contacts were screened, in whom 61 were infected. The secondary attack rates in 3841 close contacts was 1.59%. The secondary attack rate in household contacts was 65% in 8 family clustering (95% CL: 20%-100%). Three mass gathering were identified in a local recreation center box, a wedding ceremony and a family feast for new home, in which the attack rates were 63.64%, 9.38% and 12.16%, respectively. Transmission firstly occurred in the people attending the activity in the recreation center box. At least 5 generations of transmission were identified in the outbreak. The results of genome second generation sequencing of the isolates from 20 infection cases revealed that the pathogen of the outbreak was SARS-CoV-2 Omicron variant (BA.2). Conclusion Analysis on the cases caused by Omicron variant (BA.2) indicated early prevention measures are important for the control of further spread of COVID-19.
ABSTRACT
Objective: To analyze the epidemiological characteristic and tracing process of an outbreak of COVID-19 in a sea-land border city (D city) of Guangxi in December 2021, and provide scientific data for for the emergency management and scientific traceability of similar outbreaks in the future. Methods Epidemiological investigation of cases was carried out under the guideline of the Novel Coronavirus Epidemiological Investigation Programme on Cases of Pneumonia (Edition 8). RT-PCR method was used for samples testing. Furthermore, positive samples were analyzed by whole-genome sequence and phylogenetic analysis. R software 4.1.3 version was used for data analysis. Results There were 20 cases in this outbreak which related 6 families. The average incubation period was (4.6..2.2) d. Compared with the Wuhan reference strain (NC_045512), the genome sequence analysis showed that there were 35-36 nucleotide mutation sites in the novel Coronavirus genome sequence of 19 local cases, which belonged to VOC/Delta variant strain (AY.57 evolutionary branch). The 11 amino acid mutation sites were the same in all the novel Coronavirus spikes (S) proteins, which were highly homologous to the 2 COVID-19 genome sequences uploaded from a neighboring country in the GISAID genome database. Conclusion This outbreak was caused by fishermen who were infected by contacting with persons of neighboring country in the public sea area and causing located community transmission. The management of border villagers and the monitoring of epidemic strains should be strengthened to detect and deal with the outbreak as early as possible in the future.