I have a differential equation
$$\frac{dB}{dt}=\epsilon I-\delta B.$$ I want to understand why $B \leq \frac{\epsilon}{\delta}.$
$B$ is the concentration of a virus in the environment, $\epsilon$ is the rate at which infectious individuals $I$ shed virus onto the environment and $\delta$ is the rate at which virus is removed from the environment by sanitation.
Why is it that saturation of virus concentration is $\frac{\epsilon}{\delta}$?