“…The simplest forms of these models are ordinary differential equations (O.D.E) [14,15]. In recent years, epidemic models described by ordinary differential equation have been studied and extended by many authors ( see, for examples [5,12,18,25,26,30,31,32] and references cited therein). In [23] a system of ODEs with a general incidence term f(S,I) is studied, conditions are found on f under which the standard threshold behaviour occurs;the disease free equilibrium is globally asymptotically stable for R 0 < 1 and endemic equilibrium is globally asymptotically stable for R 0 > 1.…”