Through extending the basic SIR model, you can also model vector-borne diseases. Capturing VBD transmission in this way is slightly more complex than modeling diseases without vectors, because you must include both the host and the vector within the model. The Ross-Macdonald model is widely used by epidemiologists and modelers to capture the dynamics of vector-borne diseases. As with previous SIR models, individuals within the host population can be classified as susceptible, infected, or recovered from an infection. In this case, dengue. While dengue has multiple serotypes for simplicity, we'll focus on only one. In this demonstration, you'll learn how to develop the vector sections within the model. Firstly, notice how there is no recovered compartment for a vector. This is because vectors of dengue remain infectious for life. At this stage, it is necessary to distinguish between the vector and host compartments, V for vector, and H for host. For human hosts to become infected, they must be bitten in buying infectious mosquito. Likewise, for a susceptible vector to be infected with dengue, they must take a blood meal from an infectious host. This means you must draw interaction events between both sections of our model. These interactions represent disease transmission events, and disease transmission is influenced by a number of parameters. One of these important parameters is the biting rate. This corresponds to the number of bites or blood meals a mosquito takes over a given time period, let's say days. This can be calculated using the following equation, where n represents the number of blood meals taken in a given day. Next, you need to include two additional probability parameters within the model, b_h and b_v represent the probability of an infection passing from either a vector to a host, or a host to a vector. You then need to include the vector mortality rate in the model. You can exclude the host mortality rate within this model, as its magnitude is lower than the mortality rate of the vector, which is essentially negligible. Finally, you can include r within the model, and this represents the recovery rates of an infected human host. Another parameter of great importance is the parameter h. This corresponds to the proportion of blood meals a vector takes from a host. This is necessary because some vectors feed off multiple hosts, which in turn influences the probability of disease transmission between vector and host. The principle transmitter of dengue is Aedes aegypti, which takes all its blood meals from human hosts. Therefore, you can assign the value of one to h, meaning it does not need to be included within our model. As you've seen there are additional parameters you must consider when developing SIR models for VBDs. In the next demonstration, you'll see how to solve your models using differential equations.