Let $S(t)$ be the number of susceptibles to some disease, $I(t)$ the number of infected individuals and $A(t)$ the number of those who are diseased. Furthermore, let $N(t)=S(t)+I(t)$. The model is as follows:
$$ \frac{dS}{dt} = p\lambda [\epsilon I(t-a)+S(t-a)]-\frac{w(t)SI}{N}-\mu S $$
$$ \frac{dI}{dt}=\frac{w(t)SI}{N}-(\gamma+\mu)I $$
$$ \frac{dA}{dt}=\gamma I - (\tau + \mu)A, $$
where $w(t)$ is the variable force of infection. Currently the other variables aren't important for my question.
I am wondering how to interpret the term $$ -\frac{w(t)SI}{N} $$ in the first equation? Is it the rate at which those who are susceptible get infected?