Modelling the incidence and transmission dynamics of the Hepatitis A virus

Jesus Cantu, a Sociology major from Princeton University, worked with Drs. Tobias Brett and Pejman Rohani to model Hepatitis A infection.

Abstract: Hepatitis A is an acute infectious disease caused by the hepatitis A virus (HAV). In the US, an incremental approach to vaccination was initiated after the vaccine became available in 1995. In effect, a continuous decline has been experienced in the overall HAV incidence from 6.0 cases per 100,0000 individuals in 1999 to 0.4 cases per 100,000 individuals in 2011. Recently, an increasing trend in the proportion of HAV cases who were hospitalized was observed, in the US, from 7.3% in 1999 to 24.5% in 2011. Asymptomatic and non-jaundiced HAV-infected persons, especially children, have previously been identified as an important source of HAV transmission. However, the number of asymptomatic HAV-infections, through time, and their role in sustaining transmission have not clearly identified. To answer these questions, we constructed a mechanistic SIR-model with high and low risk classes implemented as a system of ordinary differential equations which were numerically integrated in R. Particular attention was placed on the effect of the implementation of different vaccination strategies on disease burden and transmission. Preliminary results show that infections from low risk individuals contribute negligibly to the number of symptomatic cases.

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