| Objectives:To analyse the epidemiological characteristics of four local COVID-19 epidemics in Guangzhou,and dynamic model of infectious disease was used for quantitative evaluation of Non-pharmacological Interventions(NPIs),to provide a scientific basis for the deployment of prevention and control measures and surveillance in the post-COVID-19 era.Methods:A total of 995 locally infected patients were included in the COVID-19 case database of Guangzhou Center for Disease Control and Prevention from January 2020 to May 2022,and they were divided by source into 366 cases associated with Hubei Province,207 cases associated with African entry,153 cases associated with Delta variant and 269 cases associated with Omicron variant.A cross-sectional study was conducted to describe the epidemic characteristics of four local COVID-19 outbreaks based on investigation reports.Meanwhile,the infectiousness indexes were analyzed based on Log-normal distribution,Gamma distribution and Weibull distribution.Finally,SEIR-VPQ model was used to simulate the data of cases associated with Delta variant,and the effectiveness of Hierarchical and classified prevention and control measures(HCPCM),vaccination and other measures was evaluated.Results:(1)Local epidemiological characteristics of COVID-19 in Guangzhou:Hubei associated epidemic,Delta variant associated epidemic and Omicron variant associated epidemic were mainly female,accounting for 51.6%,58.8%and 54.3%,Africa associated epidemic were mainly male(69.6%).The associated epidemic of Hubei and Delta Variant were mainly housework/unemployed(32.2%),(19.0%)and leaving/retired people(20.2%),(32.0%).The associated epidemic of Africa and Omicron variant were mainly commercial services(62.3%),(24.9%).79.0%of the cases were aged 18-65 years associated with Hubei Province epidemic,72.9%of the cases were aged 18-40 years associated with Africa entry epidemic,and the majority of Delta variant associated cases were ≥41 years old(64.7%).The majority of Omicron variant associated cases were 18-65 years old(81.0%).In the associated epidemic of Hubei,fever(71.6%)was the main complaint of the first symptom of the confirmed cases,while the other three cases showed no obvious discomfort(55.6%,28.1%and 55.5%,respectively).The traditional way of seeking medical treatment for fever has changed to active community investigation and management of close contacts.Most of the related cases in Hubei Province sought medical treatment voluntarily(44.3%),while the other three epidemics focused on community investigation(58.5%,27.5%and 37.9%,respectively)and management of close contacts(33.3%,67.3%and 50.9%,respectively).The median(P25,P75)of onset-report date interval of four epideimcs were 6.7(3.7,9.7)d,2.7(1.8,3.8)d,2.0(1.1,3.6)d,2.0(1.4,3.0)d,respectively.The clusters of 4 outbreaks were 232cases,121cases,132cases,and 253 cases,and the proportion of family gathering was 93.5%,66.1%,52.3%and 50.2%,respectively.(2)Estimation of indicators of infectivity:The median(P25,P75)of the incubation periods were 5.733(3.597,8.279)d,5.527(3.307,8.287)d,5.067(3.668,7.001)d and 3.230(2.268,4.434)d,respectively.The median(P25,P75)of the generation time were 4.696(3.437,6.417)d,4.935(2.815,7.683)d,1.979(1.437,2.725)d and 2.377(1.753,3.223)d.R0(95%CI)were 3.99(2.83-5.60),6.29(3.12-11.75),3.54(2.43-5.40)and 2.21(1.91-2.57).(3)Application of SEIR-VPQ model:Considering HCPCM,the phased fitting parameter β,the fitting evaluation indexes R2 of "daily cumulative number of cases"and "daily new number of cases" were 0.997 and 0.774,indicating that the model was well fitted.Rt decreased from 3.102 in the early period to 0.077,and virus transmission tended to end.The model showed that the simulated cases increased by 211.76%to 368.63%compared with the actual observed cases under different case management and control capabilities.The simulated data of no vaccination,0.5 times vaccination rate and 2 times vaccination rate increased by 122.22%～875.82%,increased by 52.94%～516.99%and decreased by 34.64%～74.51%compared with the actual observed values,respectively.The number of cases without personal protection will increase by 233.33%～5006.54%;The HCPCM for 3 days in advance,3 days in delay and 7 days in delay were reduced by 70.59%to 84.96%,increased by 245.10%to 1758.82%,increased by 969.93%to 8498.69%compared with the actual cases,respectively.Relaxation of NIPs resulted in an increase of 1273.86%～6716.34%in cases.Conclusions:There were statistically significant differences in demographic characteristics,clinical characteristics,case reports and clustering among the four local outbreaks(all P<0.05).The epidemic of mutant strains will shorten the incubation period and generation time,but considering the influence of prevention and control measures,R0 will decrease.These results suggest that the local COVID-19 epidemic may change due to different sources of infection,long-term influence of mutant strains and adjustment of prevention and control strategies.Finally,It is more effective to focus on individual protection and deploy prevention and control measures timely at the national or social level. |
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