The hosts were also divided into four compartments: susceptible hosts (SH), exposed hosts (EH), infected hosts (IH), and removed hosts (RH). The birth rate and death rate of hosts were defined as nH and mH. In this model, we set ɅH = nH × NH where NH refer to the total number of hosts. The incubation period of host infection was defined as 1/ωH and the infectious period of host infection was defined as 1/γH. The SH will be infected through sufficient contact with IB and IH, and the transmission rates were defined as βBH and βH, respectively.