Dynamic epidemic model for influenza with clinical complications

To incorporate clinical complications in the susceptible-infectious-recovered model to estimate parameters needed in dynamic changes of infectious diseases and to further evaluate the impact of disease-controlling methods.

We developed a new extended epidemic model that incorporates of disease-related complications. This model was applied to empirical data on influenza during the epidemic season of 2001-2002 in Taipei County, Taiwan, to estimate the transmission parameters that were converted to the basic reproductive rate (R(0)). The proposed model, in conjunction with estimated parameters, was applied in quantifying the efficacy of different preventive strategies.

During the study period there were 5 outbreaks of influenza. The estimated transmission probability for outbreak 1 was 0.135, with corresponding estimate of R(0), 2.7; for outbreak 2, 0.165, with estimated R(0), 3.3; for outbreak 3, 0.15, with R(0), 4.5; for outbreak 4, 0.165, with R(0), 5; and for outbreak 5, 0.165, with R(0), 5. The efficacy of antiviral prophylaxis to reduce the total episodes was 18% (95% CI, 15%-21%) under the coverage rate of 30%, 31% (95% CI, 26%-36%) under the coverage rate of 50%, and 73% (95% CI, 59%-90%) under the coverage rate of 80%. The corresponding figures for the efficacy of vaccination were 17% (95% CI, 15%-20%), 41% (95% CI, 35%-48%), and 76% (95% CI, 61%-95%). Combination of both methods would yield efficacy of 32% (95% CI, 28%-38%), 59% (95% CI, 49%-71%), and 88% (95% CI, 66%-118%), respectively.

We demonstrate how to apply a novel extended model to empirical surveillance data of an influenza study for estimating parameters pertaining to dynamic changes in the infection process. These parameters were further used to evaluate the impact of antiviral prophylaxis alone, vaccination alone, or the use of both methods.