Analysis of this model reveals that there are four equilibria, one
of them is the disease-free, the other three equilibria correspond to the presence
of single serotype respectively, and the coexistence of two serotypes.
Stabilityanalysis of each equilibria and their relations with type reproductive numbers
are shown.
We also discuss the ratio between total number of severe DHF compartment with respect to the total number of first infection compartment and
the total number of secondary infection compartment, respectively. This ratio
is needed for practical control measure in order to predict the “real” intensity of
the endemic phenomena since only data of severe DHF compartment is available
in the field