Objective To investigate the effects of perfluorochemical ( PFC) on in vitro long-term hypothermic heart preservation in rats. Methods Thirty Wistar rats were randomly divided into control group ( Celsior solution), Celsior + O_2 group (Celsior solution plus oxygen) and PFC/Celsior + O_2 group (two-layer method plus oxygen) , with 10 rats in each group. Langendorff model of isolated rat heart was prepared. The isolated heart was preserved at 4 ℃ for 8 h, and hemodynamic parameters, coronary effluent flow, and leakage of creatine kinase ( CK), lactate dehydrogenase ( LDH) and aspartate transaminase (AST) were detected after reperfusion. Besides, the myocardial ultrastructure was also observed. Results Compared with control group and Celsior + O_2 group, the left ventricular developed pressure and ± dp/dt in PFC/ Celsior + O_2 group significantly increased ( P < 0.01), while LDH, CK and AST leakage significantly decreased ( P < 0.01). However, there was no significant difference in the above paramters between Celsior + O_2 group and control group (P>0.05). Compared with control group and Celsior + O_2 group, the impairment of myocardial ultrastructure in PFC/ Celsior + O_2 group after hypothermic preservation was alleviated. Conclusion PFC as a supplementation to oxygen in heart preservation solution could enhance myocardial protection during in vitro long-term hypothermic heart preservation in rats via the improvement of energy metabolism.

Objective To establish the swine acute heart failure model for surgical experiment, and evaluate the heart function by continuous cardiac index (CCI). Methods Swine heart failure model was attempted to establish by coronary ligation in six swines. CCI was obtained by Swan-Canz catheters and Vigilance monitor, and hemodynamic, biochemical and ultrasonocardiographic results were utilized to evaluate the changes of heart function. Results Five swines accomplished the experiment. Compared with basic status, there were significant differences in mean arterial pressure (MAP) , pulmonary artery systolic pressure (PASP), mixed venous oxygen saturation ( SVO_2) and CCI for swines with heart failure ( P < 0.05) , there was no significant change in biochemical parameters, while left ventricle ejection fraction ( LVEF) significantly decreased (P<0.05). Conclusion CCI is feasible in monitoring and evaluating heart function of animal model. The swine acute heart failure model established by coronary ligations can meet the needs of surgical experiment in principle.

Objective:To investigate the epidemiological and clinical characteristics of a case infected with avian influenza A (H5N6) virus associated with exposure to aerosol and provide evidence for the prevention and control of human infection with avian influenza virus.Methods:Epidemiological investigation was conducted to identify the history of exposure, infection route, and disease progression. Real-time fluorescent quantitative RT-PCR was used to test the samples collected from the case, close contacts, environment and poultry market.Results:The case had no history of exposure to live poultry and poultry market. But before the onset the case had a history of exposure to the live poultry placed in a car with doors and windows closed. The samples collected from the case’s lower respiratory tract and the remaining frozen chicken meat were all influenza A (H5N6) virus positive.Conclusions:The source of infection was the live poultry, and the infection route might be the exposure to aerosol in a car with doors and windows closed, where the poultry were temporarily stored. It is necessary to promote centralized poultry slaughtering, cold chain distribution and fresh poultry sale, as well as strengthen health education and establish the concept of consuming fresh poultry.

Objective:To analyze the contagiousness and secondary attack rate of 2019 novel coronavirus in cluster epidemics in Guangzhou and provide evidence for the prevention and control of COVID-19.Methods:All the individuals identified to be infected with 2019-nCoV in Guangzhou, including confirmed cases and asymptomatic cases, were included and classified as imported cases and local cases. The first case of each cluster epidemic was defined as index case, and the number of subsequent infections was calculated to evaluate the contagiousness and secondary attack rate of 2019 novel coronavirus in the shortest incubation period of 1-3 days.Results:As of 18 February, 2020, a total of 349 cases of 2019-nCoV infection, including 339 confirmed cases (97.13 %) and 10 asymptomatic cases (2.87 %) were reported in Guangzhou. There were 68 clusters involving 217 2019-nCoV infection cases (210 confirmed cases and 7 asymptomatic cases). The median number of subsequent infections caused by an index case in a cluster epidemic was 3, among which 2 were confirmed cases and 1 was asymptomatic cases, respectively. The average number of contagiousness was 2.18 in shorted incubation period of 1-3 days (The average number of infected cases were 2.18 cases by the index case in a cluster epidemic), the average infection number in family members was 1.86, and the infection ratio of family member transmission was 85.32 % (1.86/2.18). The secondary attack rate in close contacts with shortest incubation period of 1-3 days was 17.12 %-18.99 %, the secondary attack rate in family members was 46.11 %-49.56 %. Conclusions:The cluster epidemic of COVID-19 in Guangzhou mainly occurred in families, the contagiousness was high. It is necessary to strengthen the prevention and control to reduce the community transmission of COVID-19.

Objective:To establish a rapid pipeline for whole genome sequencing of Chikungunya virus (CHIKV) by combining imbricated multiplex-PCR amplification and Illumina high-throughput sequencing platform.Methods:The primary reference sequences of CHIKV were downloaded from the National Center for Biotechnology Information (NCBI) database, covering all genotypes of CHIKV. After multiple alignments using the Mafft software and phylogenetic analysis, the 20 CHIKV references were selected for primer design. The Primal Scheme tool and Geneious Prime software were used to design, evaluate and optimize the primer panel. Finally, seven CHIKV-positive samples were involved in the validation of the primer panel.Results:All the amplicons of the designed panel were generated successfully. The consensuses generated from the mapping results could cover 100.00% of the coding region of the CHIKV genome when the Ct-value of the sample was less than 33, as the percentage would decrease to 99.38% when the Ct-value reached 35. The mapping percentage could be increased by 5.70%-25.43% when using the stepwise correction mapping strategy.Conclusion:The multiplex-PCR amplification method for CHIKV whole genome sequencing is relatively simple and convenient, which only requires two tubes of PCR amplification and performs well on CHIKV-positive clinical samples with different concentration levels of virus.

Objective:To establish a rapid pipeline for whole genome sequencing of Chikungunya virus (CHIKV) by combining imbricated multiplex-PCR amplification and Illumina high-throughput sequencing platform.Methods:The primary reference sequences of CHIKV were downloaded from the National Center for Biotechnology Information (NCBI) database, covering all genotypes of CHIKV. After multiple alignments using the Mafft software and phylogenetic analysis, the 20 CHIKV references were selected for primer design. The Primal Scheme tool and Geneious Prime software were used to design, evaluate and optimize the primer panel. Finally, seven CHIKV-positive samples were involved in the validation of the primer panel.Results:All the amplicons of the designed panel were generated successfully. The consensuses generated from the mapping results could cover 100.00% of the coding region of the CHIKV genome when the Ct-value of the sample was less than 33, as the percentage would decrease to 99.38% when the Ct-value reached 35. The mapping percentage could be increased by 5.70%-25.43% when using the stepwise correction mapping strategy.Conclusion:The multiplex-PCR amplification method for CHIKV whole genome sequencing is relatively simple and convenient, which only requires two tubes of PCR amplification and performs well on CHIKV-positive clinical samples with different concentration levels of virus.

Objective:To analyze the characteristics of spread and genetic evolution of H5 subtype avian influenza virus in Guangzhou from 2014 to 2019.Methods:H5 subtype virus was detected by fluorescence quantitative RT-PCR from the environmental samples in Guangzhou poultry markets. The genes of HA and NA of 48 isolates randomly selected were sequenced, including 46 isolates from environmental samples and 2 isolates from cases. The characteristics of molecular variation and genetic evolution were analyzed by using bioinformatics software.Results:A total of 1 094 strains of H5 subtype avian influenza virus were isolated from 52 284 samples (2.09%). All the strains belonged to Clade 2.3.4.4.C. NA gene belonged to H6N6 of Eurasian lineage. The cleavage sites of all the strains showed the characteristics of highly pathogenicity. Receptor binding sites were avian-derived receptors. However, mutations of S123P, S133A and T156A occurred, which implied that these strains could tend to bind to human receptors. There was an additional glycosylation site at 140 in strains isolated after 2017. The variation of antigen loci mainly occurred in B and E regions.Conclusions:H5 subtype avian influenza virus spread in Guangzhou from 2014 to 2019 with annual increased proportion of positive rate, and the sequencing results indicated that it belonged to Clade 2.3.4.4.C of H5N6 highly pathogenic virus, and genetic evolution and mutation continued, especially the common mutations which could enhance the binding capacity to human receptors. It is necessary to strengthen the surveillance.

Objective:To isolate the influenza A (H3N2) viruses from different sources in Guangzhou in 2019 and analyze these viruses' evolution and variation characteristics.Methods:The hemagglutinin (HA) and neuraminidase (NA) genes of H3N2 isolates from outpatient monitoring, influenza outbreaks, and inpatient severe cases in Guangzhou in 2019 were sequenced. Bioinformatics software analyzed the variations and evolution characteristics of HA and NA genes.Results:The epidemic peaks of influenza A (H3N2) viruses were made up of period Ⅰ (from January to August) and period Ⅱ (from November to December). The positive rate of influenza A (H3N2) in males was 13.46% (703/5 221), which was higher than that in females (11.50%, 510/4 435) ( χ 2=8.43, P=0.00). The group's positive rate of 10-20 years old was the highest (25.18%,665/2 641). The isolates from different sources were highly homologous and closely related to 3C.2a.1 branches, which could be further divided into three small groups of Group 1-3. Gene recombination was observed between different branches. The mutations of HA antigen sites gradually appeared from Group 1 to Group 3, leading to new antigen drift. Variations of HA antigenic sites mainly occurred in the region of A and B. The mutations of receptor binding sites of Group 1 and Group 3 viruses occurred in the anterior and posterior walls. There were two glycosylation sites lacked on region A of HA antigen observed in the isolates of Group 2-3. Conclusions:Genetic variations of H3N2 influenza viruses in Guangzhou included gene mutations and gene recombination. Under the pressure of the vaccine, the evolution of viruses was rapid. Therefore, the monitoring of molecular-related epidemic characteristics of the H3N2 influenza virus was necessary.

Objective:To identify a novel reassortant H3N2 avian influenza virus using nanopore sequencing technology and analyze its genetic characteristics.Methods:The positive samples of the H3N2 avian influenza virus, collected from the external environment in the farmers' market of Guangzhou, were cultured in chicken embryos. The whole genome was sequenced by targeted amplification and nanopore sequencing technology. The genetic characteristics were analyzed using bioinformatics software.Results:The phylogenetic trees showed that each gene fragment of the strain belonged to the Eurasian evolutionary branch, and the host source was of avian origin. The HA gene was closely related to the origin of the H3N6 virus. The NA gene was closely related to the H3N2 avian influenza virus from 2017 to 2020. The PB1 gene was closely related to the H5N6 avian influenza virus in Guangxi Zhuang Autonomous Region and Fujian Province from 2016 to 2022 and was not related to the PB1 gene of the H5N6 avian influenza epidemic strain in Guangzhou. The other internal gene fragments had complex sources with significant genetic diversity. Molecular characteristics indicated that the strain exhibited the molecular characteristics of a typical low pathogenic avian influenza virus and tended to bind to the receptors of avian origin. On important protein sites related to biological characteristics, this strain had mutations of PB2-L89V, PB1-L473V, NP-A184K, M1-N30D/T215A, and NS1-P42S/N205S.Conclusions:This study identified a novel reassortant H3N2 avian influenza virus by nanopore sequencing, with the PB1 gene derived from the H5N6 avian influenza virus. The virus had a low ability to spread across species, but further exploration was needed to determine whether its pathogenicity to the host was affected.

Objective:To compare epidemic characteristics between severe acute respiratory syndrome (SARS) and coronavirus disease 2019 (COVID-19).Methods:The general information, including epidemiological and clinical data of the confirmed cases during the epidemic period of the two infectious diseases was collected. The data of SARS in Guangzhou was derived from the technical files of Guangzhou Center for Disease Control and Prevention (GZCDC), including the statistical report and brief report of the epidemic situation (from January 2 to May 11, 2003);The data of COVID-19 in Wuhan was derived from the epidemic data published by Wuhan health and Health Committee's official website and other publicly reported documents (from December 9, 2019 to March 11, 2020). Descriptive analysis was used for a comparativeanalysis of the time and age characteristics, the number of cases, basic reproduction number (R0), proportion of medical staff in confirmed cases (%), crude mortality, etc.Results:A total of 1 072 cases of SARS in Guangzhou were included in the study. The incidence ratio of male to female was 1∶1.26. 43 cases of death were reported with a mortality rate of 4.01%. The median age was 36 years old. The proportion of medical staff in the early stage of the epidemic was 29.04% (88 cases). As to COVID-19 in Wuhan, a total of 49 978 cases were included, The incidence ratio of male to female was 1.04∶1. The 2 423 cases of death were reported with a mortality rate of 4.85%. The median age was 56 years old. The proportion of medical staff in the early stage of the epidemic was 30.43% (42 cases).Conclusion:The COVID-19 in Wuhan has the characteristics of high incidence and wide population. However, the epidemic situation is falling rapidly, and the prevention and control strategy needs to be adjusted timely. The prevention and control of nosocomial infection should be addressed in future.