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A long-standing question in infectious disease dynamics is the role of transmission heterogeneities, particularly those driven by demography, behavior and interventions. Here we characterize transmission risk between 1,178 SARS-CoV-2 infected individuals and their 15,648 close contacts based on detailed contact tracing data from Hunan, China. We find that 80% of secondary transmissions can be traced back to 14% of SARS-CoV-2 infections, indicating substantial transmission heterogeneities. Regression analysis suggests a marked gradient of transmission risk scales positively with the duration of exposure and the closeness of social interactions, after adjusted for demographic and clinical factors. Population-level physical distancing measures confine transmission to families and households; while case isolation and contact quarantine reduce transmission in all settings. Adjusted for interventions, the reconstructed infectiousness profile of a typical SARS-CoV-2 infection peaks just before symptom presentation, with ~50% of transmission occurring in the pre-symptomatic phase. Modelling results indicate that achieving SARS-CoV-2 control would require the synergistic efforts of case isolation, contact quarantine, and population-level physical distancing measures, owing to the particular transmission kinetics of this virus.
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Objective@#To analyze the genome characteristics of an avian influenza A (H9N2) virus isolated from an 11-month-old infant, and to look for possible sources of infection.@*Methods@#Throat swabs were collected from an infant with influenza-like illness in influenza sentinel surveillance hospitals and isolated for influenza viruses using cells. The isolates were identified for influenza virus types and subtypes by the method of hemagglutination assay, hemagglutination inhibition assay and fluorescence PCR. Whole genome sequencing of the isolated virus was carried out. The genome nucleic acid sequences and the deduced amino acid sequences were analyzed by comparing the phylogenetic trees which were constructed by bioinformatics software.@*Results@#A seasonal un-typed influenza virus was isolated from the infant with influenza like illness. With fluorescent PCR method , it was identified as H9N2 subtype of avian influenza virus and the case was confirmed as a human infected with an avian influenza A(H9N2) virus. Epidemiological studies revealed that the case had no clear history of poultry contact and exposure. Blast analysis shows that eight segments of the viral genome are avian origin, and 97.5%-99.8% homology with that of viruses isolated from the live-poultry markets. The virus belongs to G57 genotype, deduced amino acid sequence analysis shows that the virus has typical low pathogenic avian influenza characteristics.@*Conclusions@#Although the case does not have a clear history of contact or exposure to poultry, molecular traceability suggests that possible sources of infection may be still from poultry.
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Objective To study the characteristics of the diseases spectrum in hospitalized children.Methods The items of main diagnosis,gender,age,etc.in the inpatients medical records home page data aged 0? 12 years old in second-level and above hospitals of Chongqing City during 2015 were performed the disease spectrum sequence and constituent ratio analysis for deeply digging the relation between the disease change trend with the age and sex.Results The top 5 main system diseases affecting children's health were respiratory system diseases (male 43.84％,female 45.74％),some conditions originated from prenatal period (male 12.01 ％,female 13.87 ％),infectious diseases and parasites diseases (male 9.48 ％,female 9.88 ％),digestive system diseases (male 9.09 ％,female 6.95 ％),injury,poisoning and some other consequences of external causes(male 6.86 ％,female 5.27 ％).Respiratory system diseases always ranked the first place,the sexual difference among various system disease was unobvious,the sequence of injury,poisoning and some other consequence of external causes was increased with the age increasing;in the ranking of respiratory system diseases,pneumonia(38.73 ％),acute bronchitis(17.29 ％) and acute tonsillitis(13.83％) were the top 3 diseases affecting children's health.Conclusion Respiratory system diseases are the concerned key point for children health promotion.The health and epidemic prevention departments should provide effective methods and measures for preventing respiratory system diseases in children.Furthermore,the targeted prevention and treatment measures should be proposed aiming at the difference of disease sequence in different age groups.
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Objective To study the correlation between EPHX2 gene rs751141 polymorphisms and coronary heart disease (CHD) in Chinese population.Methods Totally 108 patients having more than one major coronary vessel with at least 50％ stenosis defined by Coronary angiography were selected as CHD group and control group consisted of 112 healthy subjects.Rs751141 polymorphisms were detected by PCR and gene sequence.Results Three kinds of genotypes at the rs751141 were detected,and no deviation was observed from HardyWeinberg equilibrium.There was statistical difference between the two groups regarding the distribution of the genotype frequencies and the frequency of allele C (P ＜ 0.05).Conclusion It suggests that rs751141 polymorphism is associated with CHD in Chinese population and the C allele might be a risk factor of CHD.
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Objective To analyze the prevalence status and the genetic characterizations of influenza B viruses isolated in Hunan Province after pandemic influenza A (H1N1) 2009,and to explore possible reasons for the prevalence.MethodsThroat swabs were collected from outpatients with influenza-like illness in 23 sentinel hospitals of Hunan Province in 2010.Influenza viruses were isolated with Madin-Darby canine kidney (MDCK) cells and identified by haemagglutination inhibition test.The genomes of 10 selected influenza B viruses were sequenced and analyzed for phylogenetic and molecular characterization.ResultsWith the reduction of isolation of pandemic influenza A (H1N1)2009 viruses,influenza B virus became the predominant isolated strain in the first half of 2010.Epidemic viruses mainly belonged to the B/Victoria lineage,and both two lineages co-circulated.Seven out of 11 influenza outbreaks caused by type B.Ten strains were filled into 2 branches of BV and BY which were classified by their lineage types in polymerase (PB2,PB1,PA),hemagglutinin (HA),neuraminidase (NA),NB,membrane protein (M1),influenza B virus membrane protein M2 (BM2),and non-structural protein (NS1,NS2) phylogenetic trees except the NP phylogenetic tree in which 10 strains were all in the BY branch.Compared with World Health Organization (WHO) vaccine strains,the amino acid identity of 11 proteins of the 10 strains was high (97.2％-100.0％).However,some amino acid point mutations were found.No mutation was found in drug resistance mutation sites.Some mutations in NA,NB,PB1,PB2 and NS2 molecules were found in 2 strains isolated from outbreaks compared with strains from sentinel surveillance.Conclusions The point mutations,insertions and genetic reassortment indicate viruses sustaining evolution,which is probably the reason for predominant influenza B viruses after pandemic influenza A (H1N1) 2009 in Hunan Province.
