“…For many decades, mathematical models have been formulated and examined to study how various epidemic diseases are controlled and spread. For example, see [22] , [23] , [24] , [25] , [26] , [27] , [28] , [29] , [30] , [31] , [32] , [33] , [34] and the references therein. To better understand the dynamics of co-infection diseases, some studies have been developed (see [21] , [35] , [36] , [4] , [37] ).…”