Analysis on epidemiological characteristics of dengue fever and E gene evolution of dengue virus in Guangzhou, 2020 / 中华流行病学杂志

Objective: To assess the incidence of dengue fever and E gene evolution of dengue virus in Guangzhou in 2020 and understand the local epidemiological characteristics of dengue fever and spreading of dengue virus. Methods: The information of dengue fever cases in Guangzhou in 2020 was collected from Notifiable Infectious Disease System of Chinese Center for Disease Control and Prevention Information System. Serum samples from the cases were detected by real-time PCR. The E gene was sequenced and analyzed. Maximum likelihood phylogenetic trees were constructed using software MEGA 5.05. The statistical analysis was conducted using software SPSS 20.0. Results: A total of 33 dengue fever cases were reported in Guangzhou in 2020, including 31 (93.94%) imported cases and 2 (6.06%) local cases. Compared with the data during 2016 to 2019, the number of cases, overall incidence and local incidence all decreased with statistically significant differences (all P<0.05). The imported cases from Southeast Asia constituted 90.32% (28/31) of imported cases. The E gene sequences and the phylogenetic trees of imported and local cases demonstrated close relationship with the virus sequences from Southeast Asian, and they were less homologous with the sequences of dengue virus isolated in Guangzhou in previous years. Conclusions: The incidence of dengue in Guangzhou in 2020 was significantly affected by the imported cases, especially those from Southeast Asian countries. The study result demonstrated that dengue fever was not endemic in Guangzhou and it was caused by imported ones.

Epidemiological characteristics of novel coronavirus confirmed cases and asymptomatic infected patients in Guangzhou / 中华微生物学和免疫学杂志

Objective:To analyze the epidemiological characteristics of novel coronavirus positive cases including confirmed cases with clinical symptoms and asymptomatic infected cases in Guangzhou.Methods:Epidemiological data were collected on the nucleic acid positive cases of COVID-19 in Guangzhou from January to September 2020. The epidemiological characteristics, the distribution of time intervals between the confirmed/isolation date and the date of the first positive detection were analyzed, at last the influencing factors for the confirmed cases and asymptomatic infected persons were discussed.Results:From January 7 to September 4 in 2020, a total of 1 097 nucleic acid positive cases were identified, including 658 confirmed cases (59.98%) and 439 asymptomatic infected cases (40.02%). Among the 658 confirmed cases, the median age was 42 years old, the cases indicated two significant peaks. one of the peaks was related to the imported and associated cases from Hubei province, and the other peak was connected with individuals from overseas. In terms of 439 asymptomatic infected cases, the median age was 32 years old. There were two stages in these cases. The first stage followed the second peak of confirmed cases, and the second stage overlapped with the confirmed cases in Guangzhou when the epidemic was in a period of normal prevention and control, mainly related to imported cases from abroad. The asymptomatic infected persons accounted for 57.32% in all the imported infected cases. In both of asymptomatic and symptomatic cases, the positive rate of pharyngeal swabs was higher than that of nasopharyngeal swabs and anal swabs. There were statistically significant differences in age, source of infection and gender composition between confirmed cases and asymptomatic infected persons ( P<0.05). Older age groups were more likely to have clinical symptoms, with ≥40 years being the risk factor for confirmed cases (OR=2.334, P=0.001), and 20-39 years less likely to have clinical symptoms (OR=0.620, P=0.047), compared with the 0-19 years old group. Compared with those infected in China, those infected abroad were less likely to develop clinical symptoms and became confirmed cases (OR=0.723, P=0.013). Women were more likely to have clinical symptoms than men (OR=1.574, P=0.001). Conclusions:At present, asymptomatic infected persons and confirmed patients with clinical symptoms co-existed, and the number of asymptomatic infected patients was higher than that of confirmed cases in Guangzhou. High age, domestic infection and female may be risk factors for confirmed cases. It was of great value to further explore these underlying mechanisms for the prevention and treatment of the COVID-19.

A molecular epidemiological survey on the outbreak of recombinant Norovirus GII.P16-GII.2 in Guangzhou city / 中华实验和临床病毒学杂志

Objective@#To find out the source and the epidemic pattern of norovirus outbreak in July, 2016 to June, 2017 in Guangzhou.@*Methods@#The stool samples and clinical information of diarrhea cases were collected by the sentinel hospitals and CDCs; a real-time RT-PCR method was used to detect the norovirus nucleic acids from the samples, the positive ones were amplified and sequenced; the partial sequences of norovirus were aligned by an online BLAST alignment, and a phylogenetic tree was constructed by a neighbor-joining method .@*Results@#A total of 854 cases with infectious diarrhea were reported by Guangzhou diarrhea surveillance network from July, 2016 to June, 2017; the gender ratio (male versus female) was 1∶0.67; 78.33% of the cases were preschool children under the age of 7 years. Totally 220 samples were detected norovirus G II+ (25.76%, including 5 double-positive samples with G I+ ). GII.Pe-GII.4.Sydney_2012 was the prevalent genotype in the second half of 2016 (94.64%), which was replaced by GII.P16-GII.2 in the first half of 2017 (67.65%). Since September 2016, the reported number of norovirus-caused diarrhea epidemic was increased gradually; the peak of epidemic curve emerged in February to March of 2017, and the number started to decrease since April. In May to June there were only 2-3 epidemics reported monthly. All the endemics from September to November 2016 were caused by genotype GII.Pe-GII.4.Sydney_2012; the endemics from December 2016 to April 2017 were mainly caused by genotype GII.P16-GII.2. Some samples from kitchen workers and babysitters were detected GII+ , which was consistent with the result of the cases′ samples.@*Conclusions@#It was the first time that the novel GII.P16-GII.2 recombinant strain outbroke occurred in Guangzhou City and homology analysis also suggested that GII.P16-GII.2 was the main source of those epidemics in 2016 -2017 winter and spring season. Furthermore, The kitchen workers and babysitters may have played an important role in the spread of norovirus.

Establishment of cross priming amplification for influenza A virus (H1N1) and its clinical application / 中国人兽共患病学报

In this study ,we established Cross Priming Amplification (CPA ) technology for detection of influenza A virus (H1N1) approach ,and evaluated the method through clinical specimens .A set of specific primers were designed for CPA ac‐cording to the conservative gene sequences ,designed and realized in the same temperature reverse transcription of RNA and DNA amplification . The amplification products can be totally enclosed nucleic acid detection device for testing . Fourteen healthy pharyngeal swab specimens ,seven other respiratory viruses ,and six arboviruses strains were used as the controls .We used a method that application of gradient dilution to the H 1N1 virus strain as the control to test the sensitivity of the CPA .We also used 102 clinical pharyngeal swab specimens of H1N1 patients for detection object to evaluate the feasibility of CPA clinical detection .Results showed that the CPA reaction did not appear cross reaction on health cases samples and other viruses .The sensitivity of the CPA was approximately 10 copies/uL in the established method that exactly titer H1N1 virus strain gradient dilution test .As to the positive results among the clinical pharyngeal swab samples collected from patients at different stages after onset ,the CPA had the highest positive detection rate during the first three days after onset (100% ) .While the detection rate from day 4 to day 6 after onset was 79 .31% .After 7 days ,the detection rate was 9 .09% .The established CPA assay was a highly sensitive ,specific and reproducible approach for rapid detection of H1N1 virus ,which is conducive to the early diagno‐sis of influenza A virus (H1N1) for basic medical units .

Mapping of the B Cell Neutralizing Epitopes on ED III of Envelope Protein from Dengue Virus / 病毒学报

Dengue virus (DENV) envelope [E] protein is the major surface protein of the virions that indued neutralizing antibodies. The domain III of envelope protein (EDIII) is an immunogenic region that holds potential for the development of vaccines; however, the epitopes of DENV EDIII, especially neutralizing B-cell linear epitopes, have not been comprehensively mapped. We mapped neutralizing B-cell linear epitopes on DENV-1 EDIII using 27 monoclonal antibodies against DENV-1 EDIII proteins from mice immunized with the DENV-1 EDIII. Epitope recognition analysis was performed using two set of sequential overlapping peptides (16m and 12m) that spanned the entire EDIII protein from DENV-1, respectively. This strategy identified a DENV-1 type- specific and a group-specific neutralizing epitope, which were highly conserved among isolates of DENV-1 and the four DENV serotypes and located at two regions from DENV-1 E, namely amino acid residues 309-320 and 381-392(aa 309-320 and 381-392), respectively. aa310 -319(310KEVAETQHGT319)was similar among the four DENV serotypes and contact residues on aa 309 -320 from E protein were defined and found that substitution of residues E309 , V312, A313 and V320 in DENV-2, -3, -4 isolates were antigenically silent. We also identified a DENV-1 type-specific strain-restricted neutralizing epitope, which was located at the region from DENV-1 E, namely amino acid residues 329-348 . These novel type- and group-specific B-cell epitopes of DENV EDIII may aid help us elucidate the dengue pathogenesis and accelerate vaccine design.

Expression and identification of the functional domains of dengue virus type 1 envelope protein in 293T cells / 中华微生物学和免疫学杂志

Objective To construct a recombinant expression vector for expression of the function-al domains of dengue virus serotype 1 ( DENV1 ) envelope ( E ) protein in native soluble form. Methods The genes encoding the functional domains of DENV1-E protein (1-394 aa) were amplified with PCR and then cloned into the Psectag2B-Fc eukaryotic expression vector.The 293T cells were transfected with the recombinant vector by cationic lipid-based delivery.The cell clones expressing the fusion DENV1-E-Fc protein were screened out with 2 mg/ml of Zeocin.Immunofluorescence assay ( IFA) was performed to analyze the antigenicity and integrity of the fusion protein.The fusion proteins were purified from cell lysate with Protein-G and further identified by Western blot assay.Results The soluble form of fusion protein with a molecular weight of about 90×103 was obtained at a yield of about 25 μg per 1×107 cells.The results of IFA indicated that the fusion protein kept its integrity with right conformational epitopes.The fusion protein was successfully expressed with the advantage of good specificity as indicated by IFA and Western blot assay. Conclusion The recombinant fusion protein in soluble form was successfully expressed in eukaryotic ex-pression system, which paved the way for further investigation on the function of DENV1 E protein and its protective epitopes.

Sequence analysis of VP1 region of coxsackievirus A4 and coxsackievirus A10 in Guangzhou city, 2010-2012 / 中华预防医学杂志

<p><b>OBJECTIVE</b>To identify the enterovirus from stool samples of patients with hand, foot and mouth disease(HFMD) in Guangzhou from 2010 to 2012 and to perform phylogenetic analysis of the VP1 gene sequences of coxsackievirus A4 and coxsackievirus A10.</p><p><b>METHODS</b>A total of 5 484 samples of suspected cases of HFMD which Guangzhou Center for Disease Control received from 2010 to 2012 were collected.Virus RNA was tested by nested RT-PCR method as human enterovirus 71, coxsackievirus A16, coxsackievirus A4, coxsackievirus A10 and other enteroviruses positive, and 4 111 samples were positive. Phylogenetic tree was constructed by partial VP1 gene sequences of coxsackievirus A4 and coxsackievirus A10 to perform phylogenetic analysis.</p><p><b>RESULTS</b>In 4 111 enterovirus-positive samples, the positive rate of EV71, CoxA16, CoxA10 and CoxA4 was 35.1% (1 443/4 111) , 30.7% (1 261/4 111) , 2.0% (82/4 111),0.8% (31/4 111) respectively. Different enterovirus-positive rate was statistically significant (χ(2) = 148.34, P < 0.05) .Incidences of coxsackievirus A4 positive was highest in 3-year old children as 1.3% (7/534) , and that of coxsackievirus A10 positive was highest in 0-year old children as 3.7% (34/914) . The highest positive rate of diagnosed coxsackievirus A4 positive cases was admitted in April(2.6%, 12/460) , and the highest positive rate of diagnosed coxsackievirus A10 positive cases was admitted in August 4.3% (12/278). Phylogenetic analysis indicated that all the CoxA4 stains were divided into subtype A and subtype B, and the CoxA10 stains were divided into subtypes A, subtype B and subtype C. The VP1 gene nucleotide sequences of CoxA4 and CoxA10 this study measured both belonged to subtype A.</p><p><b>CONCLUSIONS</b>The VP1 gene nucleotide sequences of CoxA4 and CoxA10 in Guangzhou from 2010 to 2012 both belonged to subtype A.</p>

An investigation on a case of hand-foot-mouth disease caused by coxsackie-virus A6 associated with a vaccine-derived poliovirus co-infection / 中华流行病学杂志

<p><b>OBJECTIVE</b>To identify the pathogen and characteristics on a case of hand-foot-mouth disease (HFMD) caused by coxsackie-virus A6 (CA6) associated with vaccine-derived poliovirus (VDPV) co-infection.</p><p><b>METHODS</b>Field epidemiological study at the epidemic area was conducted and 16 stool samples including from the patient and close contacts were collected for isolation and identification of the enterovirus (EV). 21 stool samples from patients diagnosed as HFMD were collected in the same hospital at the same month to detect CA16,EV71, CA6 and PV by real-time RT-PCR or RT-PCR. The VP1 gene of the CA6 was amplified by RT-PCR and PCR products were sequenced and analyzed.</p><p><b>RESULTS</b>The patient showed only HFMD symptoms, but no symptoms related to acute flaccid paralysis (AFP). No EVs were isolated from 16 samples collected from the patient and close contacts. And no AFP cases were found by an active search. A total of 21 samples from patients diagnosed as HFMD were collected in the same hospital at the same month and 4 were found to be EV71, 2 were CA16 and 15 (include the patient)were CA6. Only this patient was found to have had VDPV II infection. The CA6 VP1 gene was amplified from the HFMD patient and 9 other cases from the same hospital at the same month. Nucleotide sequences of the VP1 gene among the 9 strains shared 98.9%-100.0% in homology and 96.0%-100.0% in the deduced amino acid sequences. Phylogenetic analysis of the VP1 sequences categorized the 9 strains into the same branch. There were 6 nucleotides changes including U2909A between the VP1 region of the VDPV strain of the case and Sabin II. Results from phylogenetic analysis on the VP1 sequences indicated that the VDPV strain of the case was different from other VDPVs strains isolated in the world.</p><p><b>CONCLUSION</b>This case was a HFMD which caused by CA6 co-infection with VDPV II and the VDPV was newly discovered. HFMD symptoms of the case were caused by CA6. The reason why this case did not have AFP symptoms was probably due the protective effect of IPV vaccine. No AFP cases were found by the active search for AFP cases conducted in the area, which indicated that VDPV did not cause virus circulation in this area.</p>

Effects of resting days on live poultry markets in controlling the avian influenza pollution / 中华流行病学杂志

<p><b>OBJECTIVE</b>To analyze the results of nine-round environmental specimen surveillance programs in five live poultry markets pre-, during and post the 'closing days' and to evaluate the effects of 'closing days' on live poultry markets regarding the control against avian influenza pollution.</p><p><b>METHODS</b>In January 2014, control measures including culling poultry, completely cleaning and disinfecting and a 'three-day-closing' measure were conducted in five live poultry markets which were found positive for H7N9 nucleic acid in the 1(st) round environmental specimen surveillance program. Second surveillance program was conducted after a thorough disinfection campaign was launched. Several times surveillance were conducted in one week, after the markets were reopened. RT-PCR was used to test the nucleic acid of HA, H5, H7 and H9 viruses.</p><p><b>RESULTS</b>654 specimens from the environment were collected and tested. During the first round surveillance program, positive rates for influenza A and H5/H7/H9 nucleic acid of poultry stalls appeared to be 94.44% and 61.11% respectively. The positive rates of poultry stalls reduced to 0 after the disinfection campaign but increased again after the markets reopened. The positive rate for influenza A of poultry stalls slightly increased from 50.00% in the third surveillance to 72.22% in the ninth surveillance (P > 0.05). The positive rate for H5/H7/H9 of poultry stalls showed a significantly increasing trend, from 0 in the third surveillance to 44.44% in the ninth surveillance (P < 0.01). The positive rates for influenza A and H5/H7/H9 nucleic acid of specimens were 28.89% and 17.78% respectively. The positive rate of specimens reduced to 0 after disinfection while increased again after reopening of the markets. The positive rate for influenza A of specimens slightly increased from 19.67% in the third surveillance to 27.54% in the ninth surveillance programs (P > 0.05). The positive rate for H5/H7/H9 of specimen showed a significant increasing trend, from 0 in the third surveillance to 8.70% in the ninth-round surveillance programs (P < 0.01). The positive rate for influenza A was the highest for slaughter- related specimens of 22.4% (35/156). The positive rates for influenza A from sewage and drinking water being collected on the later stage after the markets reopened (25.9%, 12.4%)were higher than those on the early stage (8.3%, 8.6%) (P > 0.05). The positive rate for influenza A of poultry stalls with overnight poultry storage (91.7%) was significant higher than that of poultry stalls without the overnight storage (33.3%). The positive rate for influenza A of poultry stalls in which simultaneously selling different kinds of poultry (85.7%) was significant higher than that of poultry stalls in which selling only one kind of poultry at one time (25.0%) (P < 0.05).</p><p><b>CONCLUSION</b>Slaughter in live poultry markets posed a large risk of pollution diffusion. Sewage and drinking water showed an accumulation effect for avian influenza virus. Overnight poultry storage and selling different kinds of poultry at one time at the poultry stalls seemed the risk factors for avian influenza virus transmission. Complete cleaning, disinfecting and several 'closing days' for live poultry markets seemed effective in eliminating avian influenza virus. Once the markets were reopened, they seemed to be soon polluted again.</p>

Establishment and preliminary application of dengue virus envelope domain III IgG antibody capture enzyme-linked immuno-absorbent assay / 中华预防医学杂志

<p><b>OBJECTIVE</b>To establish a highly sensitive and specific assay to detect dengue virus (DENV) envelope protein domain III (EDIII) IgG antibody, and to explore its value in the diagnosis and seroepidemiological survey of dengue.</p><p><b>METHODS</b>The DENV EDIII IgG antibody capture ELISA was developed using the recombinant full-length DENV EDIII, which was prepared by Pichia yeast expression system as the capture antigen. The serum samples were collected from the same group of 35 DENV-1 patients of primary infection during disease period in 2006 and their follow-up phase in 2010; and the sensitivity of the assay was compared to that of the commercial Panbio DENV IgG ELISA.</p><p><b>RESULTS</b>The sensitivity of DENV EDIII IgG ELISA in detecting the serum samples from disease period and follow-up phase was 87% (20/23) and 94% (33/35), respectively; whereas the sensitivity of Panbio DENV IgG ELISA was 71% (25/35) and 0, respectively. The sensitivity of DENV EDIII IgG ELISA in detecting the serum samples from both periods was similar, without statistical significance (χ(2) = 0.946, P = 0.331). For serum samples from disease period, the sensitivity of DENV EDIII IgG ELISA was comparable with that of Panbio DENV IgG ELISA (χ(2) = 1.924, P = 0.165). However, DENV EDIII IgG ELISA demonstrated a significantly higher sensitivity than Panbio DENV IgG ELISA in detecting the serum samples from follow-up phase (χ(2) = 62.432, P = 0.000).</p><p><b>CONCLUSION</b>DENV EDIII IgG capture ELISA is highly sensitive in detecting IgG in the serum samples from either disease period or follow-up phase. This method might be a promising alternative for diagnosis and seroepidemiologic survey of dengue.</p>

Evaluation on the risks of H5, H7 and H9 avian influenza infections in Guangzhou: using data from the 2006-2012 avian influenza surveillance program / 中华流行病学杂志

<p><b>OBJECTIVE</b>To analyze the results of avian influenza surveillance program in Guangzhou from 2006 to 2012 and to evaluate the risk of infections with H5, H7 and H9 subtypes avian influenza viruses.</p><p><b>METHODS</b>Avian influenza surveillance system in Guangzhou consisted five components:serum surveillance on occupational population, environmental specimen surveillance of avian influenza virus, avian flu emergency surveillance, influenza viruses surveillance on ILI patient and surveillance on pneumonia of unknown causes. Hemagglutination inhibition test was conducted to detect the antibodies against H5, H7 and H9 while RT-PCR was used to test the nucleic acid of H5, H7 and H9 viruses.</p><p><b>RESULTS</b>From 2006 to 2012, 4103 serum specimens were collected from occupational populations and the overall positive rate of H5/H7/H9 antibodies was 3.82% . The antibody positive rates for H5, H7 and H9 were 0.22% ,0.00% and 3.70% respectively. 4 serum specimens for H5 and H9 simultaneously showed antibody positive. The positive rate of H9 among occupational populations(4.21%)appeared higher than that from the control population(2.16%). 2028 specimens were collected from poultry sites and 55 samples found positive for H5 nucleic acid (positive rate:2.71%), 14 samples positive for H9 nucleic acid (positive rate:0.69%), 5 specimens, simultaneously positive for H5 and H9 nucleic acids. However, none of the samples showing H7 nucleic acid positive. From 2006 to 2012, all the tested H5/H7/H9 virus were negative from the respiratory/serum specimens among those close contacts of patients or high risk groups through the avian flu emergency surveillance program,ILI patient influenza virus surveillance programs or pneumonia of unknown causes surveillance program.</p><p><b>CONCLUSION</b>Contamination of H5/H9 avian influenza virus did exist in the poultry sites in Guangzhou, especially in the wet Markets. The H5/H9 avian influenza virus caused asymptomatic infection was proved to be existed within the population exposed to the poultry, suggesting that the poultry occupational population in Guangzhou was under the risk of avian influenza virus infection.</p>

Risk evaluation on H7N9 avian influenza in Guangzhou, China / 中华流行病学杂志

<p><b>OBJECTIVE</b>We conducted both quick surveillance and evaluation programs within one week after the novel H7N9 influenza cases had been released by the Ministry of Health (MOH), to get the basic information on H7N9 virus in Guangzhou.</p><p><b>METHODS</b>We sampled live birds from food markets and the natural habitat of birds to detect H7N9, H5 and H9 viruses. We interviewed workers from both markets and natural habitats. We also reviewed records on pneumonia patients with unknown causes from the surveillance system, to find clues related to the identification of severe pneumonia.</p><p><b>RESULTS</b>We sampled 300 specimens from 49 stalls in 13 food markets and a natural habitat but none showed H7N9 positive result. A chopping block was detected positive of carrying H5 avian influenza virus, while another 4 specimens including a chicken cage, a duck cage, a chopping block and a pigeon cage were detected positive of carrying H9 avian influenza virus. In the past month, no sick, dead birds or ILI cases among the workers were discovered. 21.2% (7/33) of the stalls did not follow the set regulations for prevention. 10.3% (4/39) of the stalls had the cages cleaned, 4 days after the inspection. 3.7% (2/54) of the workers wore masks and 40.7% (22/54) of them wore gloves during the slaughtering process. 102 bird feces specimens were tested negative on H7N9 virus. No pneumonia cases with unknown reason were identified. From April 3(rd) to 17(th), we found 26 severe pneumonia cases but with negative results on influenza A (H7N9).</p><p><b>CONCLUSION</b>According to the data and information from 1) lab tests, 2) pneumonia cases with unknown reasons under the surveillance system, 3) the identification of severe pneumonia cases, and 4) preventive measures and actions taken by the workers, we inferred that no H7N9 virus or related cases were found prior to April in Guangzhou. However, the risk of H7N9 epidemic does exist because of the following reasons:1) improper market management process, 2) negligent behavior of the workers and 3) potential trend of the national situation, suggesting strategies related to poultry markets management, health education and preventive measures against the avian influenza need to be strengthened.</p>

Dengue Fever epidemiological status and relationship with meteorological variables in Guangzhou, Southern China, 2007-2012 / 生物医学与环境科学（英文）

Ecological methodology plus negative binomial regression were used to identify dengue fever (DF) epidemiological status and its relationship with meteorological variables. From 2007 to 2012, annual incidence rate of DF in Guangzhou was 0.33, 0.11, 0.15, 0.64, 0.45, and 1.34 (per 100 00) respectively, showing an increasing trend. Each 1° C rise of temperature corresponded to an increase of 10.23% (95% Cl 7.68% to 12.83%) in the monthly number of DF cases, whereas 1 hPa rise of atmospheric pressure corresponded to a decrease in the number of cases by 5.14% (95% Cl: 7.10%-3.14%). Likewise, each one meter per second rise in wind velocity led to an increase by 43.80% or 107.53%, and one percent rise of relative humidity led to an increase by 2.04% or 2.19%.

Analysis of serum neutralizing antibody response in patients with primary dengue virus type 1 infection / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the characteristics and dynamic changes of serum neutralizing antibody response in patients with primary infection of dengue virus type 1 (DENV-1).</p><p><b>METHODS</b>Serum samples were obtained from the same patients with primary infection of DENV-1 within 2 weeks after symptom onset in 2006 and in 2010. A group-specific DENV NS1 capture ELISA-based micro-neutralizing test (ELISA-MNT) capable of detecting neutralizing antibodies against all the 4 serotypes of DENV was used to test the neutralizing antibody titers against DENV in the serum samples. The neutralizing antibody titers against a standard strain and 2 clinically isolated strains of DENV-1 were detected in serum samples collected in 2010.</p><p><b>RESULTS</b>Cross-reactive neutralizing antibody response against all the 4 serotypes of DENV was found in both of the serum samples collected in 2006 and 2010, but the samples collected in 2006 showed stronger cross-reactive neutralizing antibody responses. The neutralizing antibody against DENV-2, rather than the anticipated DENV-1 antibody, had the highest titer in the samples collected in 2006, whereas the antibody against homologous DENV-1 had the highest titer in the samples obtained in 2010. The neutralizing antibody titers against the homologous DENV-1 was significantly higher in samples collected in 2010 (U=86.500, P=0.000), which also demonstrated significantly different neutralizing antibody titers against the 3 different strains of DENV-1 (Χ(2)=12.123, P=0.002).</p><p><b>CONCLUSION</b>The production of cross-reactive neutralizing antibodies between the 4 serotypes of DENV is a characteristic of DENV infection, particularly during early infection, but only the homologous neutralizing antibody increases obviously over time. The titers of the neutralizing antibodies against different strains, even of the same serotype, may differ distinctly.</p>

Envelope gene evolution analysis on type 1, 2, 3 dengue virus in Guangzhou in 2010 / 中华传染病杂志

ObjectiveTo analyze the Envelope (E) gene of type 1,2,3 dengue virus isolated fromGuangzhouin2010, andtoinvestigatetheinfectionsourceandvirusgenotypes.MethodsEighty-five serum samples were collected from 85 patients in acute phase of dengue fever.Dengue virus was cultured and isolated by C6/36 cells.The whole length of E gene was amplified by reverse transcriptase-polymerase chain reaction (RT-PCR) and then sequenced.The phylogenetic tree was drawn by neighbor-joining method.The bioinformatics analysis was performed by combining the phylogenetic information and the epidemiologic data.ResultsSix strains of type 1 dengue virus,two strains of type 2 dengue virus and six strains of type 3 dengue virus were isolated from 85 samples.The E gene sequence of these strains was obtained by sequencing.The phylogenetic analysis showed that type 1 and 3 dengue virus belonged to two genotypes (Asian and South Pacific ocean,India subcontinent and Southeast Asia/South Pacific ocean,respectively),and type 2 dengue virus belonged to one genotype (Malaysia/India subcontinent).ConclusionIt's presumed that all strains of type 2 dengue virus are imported,four strains of type 1 dengue virus are imported and four strains of type 3 dengue virus arc imported,the remaining two stains of type 1 and two stains of type 3 dengue virus need mosquito intermediary research further to prove their origins.

Investigation on the source of infection regarding an avian influenza (H5N1) case in Hong Kong that returning from Guangzhou / 中华流行病学杂志

Objective We conducted an epidemiologic investigation to determine the source of infection on an avian influenza (H5N1) case who returned from Guangzhou,in Hong Kong.Methods Data related to epidemiologic investigation,medical observation on close contacts,Syndromic Surveillance on poultry salesmen,emergency monitoring,detection of the samples,source tracing on potential Avian influenza virus (H5,H7,H9) infected people,situation on environment pollution by avian influenza virus in the markets etc.were gathered.The determination of infection source was through comparing the different genes between the case and positive environmental samples.Results The infected case witnessed the procedure of how a live duck was killed,in market A in Guangzhou during May 17th to 19th.The case was diagnosed as respiratory tract infection in 2 Third-grade-Class A hospitals in Guangzhou on May 23th and 24th.The diagnosis was made as Avian influenza cases on May 26th after going back to Hong Kong.23 close contacts and 34 markets poultry salesmen did not show any ILI related symptoms.However,2 poultry salesmen from the markets nearby the place where the Avian influenza case stayed,were detected having positive H9 avian influenza antibody,with the H9 positive rate as 6.06％ (2/33).Among the environmental samples in the 2 markets nearby home of the patient,chopping block was found to have carried H5,with positive rate as 9.8％(5/51) while poultry cage was found to carry H9,with the positive rate as 2.0％(1/51).A H5 positive sample was found with clade 2.3.2.1,same to the case,from a chopping block at the market B where the sources of poultry was the same as market A.Conclusion The source of infection seemed to come from the markets in Guangzhou,that calling for the strengthening of poultry market management,for avian influenza prevention.History related to contact of poultry should be gathered when a diagnosis of respiratory tract infection was made.Timely sampling and testing should be made to improve the sensitivity of diagnosis.

Epidemiological situation and the E gene evolution of dengue virus in Guangzhou, 2011 / 中华流行病学杂志

Objective To investigate the epidemiological characteristics of Dengue and the E gene of the new isolated strains.Methods Epidemiological data and serum samples were collected.Serotypes were detected by real-time PCR and virus was isolated in C6/36.E gene of the new isolated strains were sequenced and analyzed by Mega 4.0.Results The cases of Dengue reached at the peak during September and November,with Serotype 1,2 and 4 were involved.Five strains of serotype 1 were isolated,with 4 of them fell into the clad of Asia genotype,and 1 belonged to America/Africa genotype.Conclusion The strains isolated in Guangzhou showed a high identity to the Southeast Asian strains.There seemed high risk of outbreak of Dengue in this area,However,the Dengue virus might have already been localized.

Epidemiological survey and analysis on an outbreak of gastroenteritis due to water contamination / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To document the investigation and control of an outbreak of gastroenteritis in City G, South China, and provide a reference for preventing future outbreaks.</p><p><b>METHODS</b>An ambispective cohort study was designed. Attack rate (AR) and relative risks (RR) were calculated to identify the causes of gastroenteritis. Investigations using questionnaires included personal interviews with patients and doctors, reviews of medical records, laboratory examinations of fecal specimens and continuous hygiene monitoring of water samples from the waterworks.</p><p><b>RESULTS</b>Overall, 427/71534 (AR=5.97%) cases were identified between October 31 and November 12 2010. Geographic distribution was highly localized, with 80% of cases occurring in the areas supplied by waterworks-A. Consumption of water provided solely by waterworks-A was found to be associated with illness (RR=8.20, 95 CI%:6.12-10.99) compared with that from waterworks-B. Microbiological analyses confirmed the presence of Norovirus in six of eight fecal samples from symptomatic patients, two water samples from waterworks-A and two sewage samples. After taking effective measures, the hygienic indices of waterworks-A met health criteria again on November 9 and no cases were reported 3 days later.</p><p><b>CONCLUSION</b>The outbreak reported here was caused by drinking tap water contaminated with sewage at the source. Early identification of possible contamination sources and awareness of changes that might negatively impact water quality are important preventive measures to protect public health.</p>

Genetic Evolution of Neuraminidase Gene of Influenza A/H1N1 Virus / 中山大学学报(医学科学版)

[Objective]This study was designed to investigate the genetic evolution of the neuraminidase(NA)gene of seasonal A/H1N1 and 2009 novel A/H1N1 inflilenza virus,and discuss the genetic variation of influenza A virus.[Methods]The virus strains were separately isolated from the clinical samples collected in 2006 and 2009,and then identified as seasonal A/H1N1 and novel A/H1N1.The full length of the NA gene of these strains was amplified by RT-PCR.Then the genetic evolution and mutations of important functional sites were analyzed.[Results]The homology of NA gene between the 2009 novel A/H1N1 isolates and 2006 seasonal A/H1N1 isolates was low(77.9%～78.8%),so was the homology of NA gene between the 2009 novel A/H1N1 isolates and representative strains of different periods and 1979-2001 WHO recommended vaccine strains(78.1%～79.3%).But compared with the WHO recommended vaccine strains of 2009 novel A/H1N1,the homology reached more than 99%.The genetic evolution analysis revealed that NA gene of 2009 novel A/H1N1 had the closest genetic relationship with the swine influenza A virus(A/swine/Belgium/1/1983)from Eurasian Iineage,and some of the antigenic sites and neuraminidase active sites of NA gene of seasonal A/H1N1 were mutated after 2005.[Conclusion]The NA gene of 2009 novel A/H1N1 may originate from Eurasian Iineage of swine influenza virus.The variation of NA gene of seasonal A/H1N1 has occurred in a certain degree.Hence,it is very necessary to continuously monitor the variant of influenza A virus.

Analysis on envelope gene of type Ⅰ dengue virus isolated from Guangzhou area in 2009 / 中华传染病杂志

Objective To sequence and analyze the envelope (E) gene of type Ⅰ dengue virus isolated from Guangzhou in 2009 for tracing the infection source. Methods The serum samples were collected from patients diagnosed with dengue fever in Guangzhou area during 2009. Dengue virus was isolated and cultured in C6/36 cells.The whole length of E gene was amplified by reverse transcriptase-polymerase chain reaction (RT-PCR) and then sequenced. The phylogenetic tree was drawn by neighbor-joining method. The bioinformatics analysis was performed by combining the phylogenetic information and the epidemiology data. Results Four strains of type Ⅰ dengue virus were isolated from 19 samples. E gene of these strains was amplified and sequenced. The phylogenetic analysis showed that 09/GZ/9104 strain and 09/GZ/9236 strain had identical nucleotide sequence and fell within the American/African group, 09/GZ/11534 stain and 09/GZ/11562 strain had similar sequence homology and fell within the Asian group. Conclusion The typeⅠdengue viruses in Guangzhou area in 2009 are imported, which belong to two genotypes and may come from two independent origins respectively.