Dynamic Model On Strategies For Containing Influenza A(H1N1)Pandemic In Changsha

OBJECTIVES:To simulate the pandemic of influenza A(H1N1) in Changsha using a dynamical model, and assess the effect of interventions for control the pandemic including isolation, antivirus, vaccination, etc.METHODS:Based on the history of influenza A(H1N1) and the demographic characteristics of Changsha, we set up a susceptible-exposed-infectious/asymptomatic-removed (SEIAR) model to simulate an influenza A(H1N1) pandemic in Changsha city. In the SEIAR simulation, key parameters were determined by the epidemical data of influenza in Changsha. On the basis of SEIAR, we introduced’isolation’,’antivirus’,’vaccination’ and ’combimed-interventions’and constructed the susceptible-exposed-infectious/asymptomatic-removed-quarantine (SEIARQ) model, susceptible-exposed-infectious/asymptomatic-removed-vaccination (SEIARV) model and model with’antivirus’and’combimed-interventions’. The pandemic was simulated by software Matlab7.1and Berkeley Madonna8.3.18. Indicators including total attack rate (TAR) and total infection rate (TIR) were estimated to assess the efficacy of all the strategies for controlling the pandemic.RESULTS:The average incubation period of influenza A (H1N1) was2.1days, the average infectious period was5.3days.58.46%of infected people develop influenza symptoms and41.54%would be asymptomatic. Of symptomatic people,3.11%were servere cases and0.33%would die. The basic reproduction number (λ0) of influenza A (H1N1) pandemic in Changsha city was1.81. When there was not intervention, the TIR and TAR were73.98%and43.25%, respectively. Use of any single-intervention strategy would have certain efficacy. The bigger of quarantine and vaccination force were adopted, the efficacy of controlling the outbreak would be better. Forthermore, use of a combined-intervention strategy would be more effective. The orders of efficacy were the isolation+antivirus+vaccination, antivirus+vaccination, isolation+antivirus, and isolation+vaccination strategies. The real combined strategies implemented by health department were estimated to yield a TAR of27.81%which was cut off73.60%.CONCLUSIONS:SEIAR model can simulated the pandemic of influenza A(H1N1) preferably. Use of a combined-intervention strategy would be more effective than single-intervention strategy. And the efficacy of pharmacological interventions would be better than nonpharmacological ones. The isolation+antivirus+vaccination strategy could be primary intervention when an influenza pandemic happens.