Quantitative evaluation on the effectiveness of prevention and control measures against pandemic influenza A (H1N1) in Beijing, 2009 / 中华流行病学杂志

Objective To quantitatively evaluate the effectiveness of prevention and control measures against pandemic influenza A (H1N1) in Beijing, 2009 and to provide evidence for developing and adjusting strategies for prevention and control of the disease. Methods Considering the seasonality and the number of vaccination on pandemic influenza A (H1N1) , data regarding pandemic influenza A (H1N1) in Beijing were collected and analyzed. Based on the dynamics of infectious disease transmission, a quantitative model for evaluation of prevention and control measures was developed. Results Both latency and infectious periods of pandemic influenza A (H1N1) were estimated to be 1.82 days and 2.08 days, respectively. The effective reproduction numbers of the three periods were 1.13,1.65 and 0.96, respectively. Thanks to the implementation of a series of measures to prevent and control pandemic influenza A (H1N1), the cumulative number of laboratory-confirmed cases of pandemic influenza A (H1N1) was reduced, making it much smaller than what would have been under the natural situation. Specifically, the program on pandemic (H1N1) 2009 vaccination reduced the cumulative number of laboratory-confirmed cases by 24.08% and postponed the peak time. Conclusion Measures that had been taken during this period, had greatly contributed to the successful prevention and control of pandemic influenza A (H1N1). The 2009 Pandemic (H1N1)vaccination was confirmed to have contributed to the decrease of cumulative number of laboratoryconfirmed cases and postponed the peak arrival time.

Comparison between early outbreak detection models and simulated Outbreaks of measles in Beijing / 中华流行病学杂志

Objective Using simulated outbreaks to choose the optimal model and its related parameters on measles so as to provide technical support for developing an Auto Warning System(AWS).Methods AEGiS-Cluster Creation Tool was applied to simulate a range oftmique outbreak signals.Then these simulations were added to the aetnal daily counts of measles from the National Disease Surveillance System,between 2005 and 2007.Exponential weighted moving average(EWMA),C1-MILD(C1),C2.MEDIUM(C2).C3-ULTRA(C3)and space.time permutation scar statistic model were comprehensively applied to detect these simulations.Tools for evaluation as Youden's index and detection time were calculated to optimize parameters before an optimal model was finally chosen.Results EWMA(λ=0.6,κ=1.0),C1(κ=0.1,H=3σ),C2(k=0.1,H=30),C3(κ=1.0,H=4σ)and space-time permutation scan statistic(maximum temporal cluster size=7 d,maximum spatial cluster size=5 km)appeared to be the optimal parameters among these models.Youden's index of EWMA was 90.8%and detection time being 0.121 d.Youden's index of C1 was 88.7%and detection time being 0.142 d.Youden's index of C2 was 92.9%and detection time being 0.121 d.Youden's index of C3 was 87.9%and detection time being 0.058 d.Youden's index of space-time permutation scan statistic was 94.3%and detection time being 0.176 d.Conelusion Among these five early warning detection models.space-time permutation scan statistic model had the highest efficacy.