  We consider an age-structured epidemic model with two basic public health
interventions: (i) identifying and isolating symptomatic cases, and (ii)
tracing and quarantine of the contacts of identified infectives. The dynamics
of the infected population are modeled by a nonlinear infection-age-dependent
partial differential equation, which is coupled with an ordinary differential
equation that describes the dynamics of the susceptible population. Theoretical
results about global existence and uniqueness of positive solutions are proved.
We also present two practical applications of our model: (1) we assess public
health guidelines about emergency preparedness and response in the event of a
smallpox bioterrorist attack; (2) we simulate the 2003 SARS outbreak in Taiwan
and estimate the number of cases avoided by contact tracing. Our model can be
applied as a rational basis for decision makers to guide interventions and
deploy public health resources in future epidemics.
