Study on the efficacy of quarantine during outbreaks of acute hemorrhagic conjunctivitis outbreaks at schools through the susceptive-infective-quarantine-removal model / 中华流行病学杂志

To assess the efficacy of quarantine for acute hemorrhagic conjunctivitis (AHC)outbreaks control in schools,by using the Compartment Model.Through combining the characteristics of both AHC and compartment model,we built a susceptive-infective-removal (SIR) model suited for AHC outbreaks control in schools,and then quarantine was added into the model to develop a susceptive-infective-quarantine-removal (SIQR) model.An outbreak of AHC in Changsha in 2011 was employed as a sample to assess the effect of quarantine for the prevention and control of AHC.Basic reproduction number (λ 0) of the AHC outbreak without intervention was 6.80,thus the transmission speed of the disease became quite fast.If no intervention had been adopted,almost all the students,faculties and staff members would have been infected within 23 days,and the accumulative cases would become 738,with the total attack rate (TAR) as 99.73％.The peak of the outbreak was at Sep.11th and the number of new cases was 126 on that day.The efficacy would have been different if quarantine forces had been taken at different time and differently.The bigger and earlier the quarantine force had been adopted,the lower morbidity peak and the smaller TAR would have been appeared,with better efficacy of outbreak control.If the quarantine rate had been taken at the level of 90％ on the sixth day,the accumulative case would have been reduced to 132 and the TAR had become 17.84％ consequently.Quarantine program could be used as a main intervention approach to be employed for ACH outbreak at schools.

Genetic analysis of the NS genes of H5N1 avian influenza viruses isolated from sewage in poultry markets / 病毒学报

In order to investigate the transmission risk of H5N1 avian influenza viruses (AIV) from sewage in Changsha poultry markets, the evolution relationship and molecular characteristics of non-structural (NS) genes of H5N1 AIV from sewage were analyzed. Nine H5N1 AIV environmental sewage specimens were collected from Changsha poultry markets. The NS genes were amplifyed by PCR and then sequenced with TA cloning. Amino acid(aa) sequence alignment and phylogenetic tree analysis were conducted by Lasergene and Mega5 software. Eight NS genes TA cloning were constructed successfully. Phylogenetic tree indicated that they were belonged to the allele A subgroup. Aa homology analysis showed 90.1% 92.5% identity in NS1 proteins and 91.0% - 92.6% identity in NS2 proteins compared with reference viruses of the allele A (A/chicken/ Hubei/ w h/ 1999). The homologies of the amino sequences of NS1 and NS2 in this study were 93.8%-100.0% and 98.4%-100.0%, respectively. The C terminal of all eight H5N1 NS1 proteins from sewage in poultry markets carried a ESEV of PL motif and the 92 amino acids were E, furthermore, the 80 to 84aa were missed which were the characteristics of highly pathogenic AIV. The NS genes of H5N1 AIV from sewage in poultry markets have molecular characteristics of highly pathogenic and have the potential risk of H5N1 virus spreading.

The warning model and influence of climatic changes on hemorrhagic fever with renal syndrome in Changsha city / 中华预防医学杂志

<p><b>OBJECTIVE</b>To realize the influence of climatic changes on the transmission of hemorrhagic fever with renal syndrome (HFRS), and to explore the adoption of climatic factors in warning HFRS.</p><p><b>METHODS</b>A total of 2171 cases of HFRS and the synchronous climatic data in Changsha from 2000 to 2009 were collected to a climate-based forecasting model for HFRS transmission. The Cochran-Armitage trend test was employed to explore the variation trend of the annual incidence of HFRS. Cross-correlations analysis was then adopted to assess the time-lag period between the climatic factors, including monthly average temperature, relative humidity, rainfall and Multivariate Elño-Southern Oscillation Index (MEI) and the monthly HFRS cases. Finally the time-series Poisson regression model was constructed to analyze the influence of different climatic factors on the HFRS transmission.</p><p><b>RESULTS</b>The annual incidence of HFRS in Changsha between 2000 - 2009 was 13.09/100 000 (755 cases), 9.92/100 000 (578 cases), 5.02/100 000 (294 cases), 2.55/100 000 (150 cases), 1.13/100 000 (67 cases), 1.16/100 000 (70 cases), 0.95/100 000 (58 cases), 1.40/100 000 (87 cases), 0.75/100 000 (47 cases) and 1.02/100 000 (65 cases), respectively. The incidence showed a decline during these years (Z = -5.78, P < 0.01). The results of Poisson regression model indicated that the monthly average temperature (18.00°C, r = 0.26, P < 0.01, 1-month lag period; IRR = 1.02, 95%CI: 1.00 - 1.03, P < 0.01), relative humidity (75.50%, r = 0.62, P < 0.01, 3-month lag period; IRR = 1.03, 95%CI: 1.02 - 1.04, P < 0.01), rainfall (112.40 mm, r = 0.25, P < 0.01, 6-month lag period; IRR = 1.01, 95CI: 1.01 - 1.02, P = 0.02), and MEI (r = 0.31, P < 0.01, 3-month lag period; IRR = 0.77, 95CI: 0.67 - 0.88, P < 0.01) were closely associated with monthly HFRS cases (18.10 cases).</p><p><b>CONCLUSION</b>Climate factors significantly influence the incidence of HFRS. If the influence of variable-autocorrelation, seasonality, and long-term trend were controlled, the accuracy of forecasting by the time-series Poisson regression model in Changsha would be comparatively high, and we could forecast the incidence of HFRS in advance.</p>

Application of Susceptible-Infected-Recovered model in dealing with an outbreak of acute hemorrhagic conjunctivitis on one school campus / 中华流行病学杂志

To simulate intervention measures in controlling an outbreak of acute hemorrhagic conjunctivitis on one school campus by using the Susceptible-Infected-Recovered (SIR) model, to provide evidence for preparedness and response to the epidemic. Classical SIR model was used to model the epidemic. Malthusian exponential decline method was employed to estimate the infective coefficient β for interventions. The initial value of parameters was determined based on empirical data. The modeling was implemented using Matlab 7.1 software. Without interventions, the outbreak was expected to experience three phrases: (1)early stage (the first 5 days) in which the epidemic developed slowly and could be intervened easily; (2) rapid growing stage (6-15 days) in which the number of infected cases increased quickly and the epidemic could not be well controlled;and (3) medium and late stage (16 days and later) in which more than 90% of the susceptible persons were infected but the intervention measures failed to prevent the epidemic. With the implementation of interventions, the epidemic was predicted to be controlled in the early stage, under the SIR model. The simulation based on the SIR model kept an acceptable consistency with the actual development of epidemic after the implementation of intervention measures. The SIR model seemed effective in modeling interventions to the epidemic of acute hemorrhagic conjunctivitis in the schools.

Spatio-temporal process and the influencing factors on influenza A (H1N1) pandemic in Changsha / 中华流行病学杂志

Objective To analyze the spatio-temporal process on 2009 influenza A (HlNl) pandemic in Changsha and the influencing factors during the diffusion process. Methods Data were from the following 5 sources, influenza A (HlNl) pandemic gathered in 2009, Geographic Information System (GIS) of Changsha, the broad range of theorems and techniques of hot spot analysis, spatio-temporal process analysis and Spearman correlation analysis. Results Hot spot areas appeared to be more in the economically developed areas, such as cities and townships. The cluster of spatial-temporal distribution of influenza A (HlNl) pandemic was most likely appearing in Liuyang city (RR=22.70,P<0.01). The secondary cluster would include districts as Yuelu (RR=6A9,P< 0.01) , Yuhua (RR=81.63, P<0.01). Xingsha township appeared as the center in the Changsha county (RR=2.90, P<0.01) while townships as Yutangping (RR=19.31, P<0.01) , Chengjiao (RR=73.14,P<0.01) and Longtian appeared as the center in the west of Ningxiang county (RR= 14.43,P<0.01) and Wushan as the center in the Wangcheng county (RR= 13.84,P<0.01). As time went on, the epidemic moved towards the eastern and more developed regions. Regarding factor analysis, population, the amount of students, geographic relationship and business activities etc. appeared to be the key elements influencing the transmission of influenza A (H1N1) pandemic. At the beginning of the epidemic, population density served as the main factor (r=0.477, P<0.05) but during the initial and fast growing stages, it was replaced by the size of students to serve as the important indicator (r=0.831, P<0.01; r=0.518, P<0.01). However, during the peak of the epidemics, the business activities played an important role (r=-0.676, P<0.01). Conclusion Groups under high risk and districts with high incidence rates were shifting, along with the temporal process of influenza A(H1N1) pandemic, suggesting that the protection measures need to be adjusted, according to the significance of influencing factors at different stages.