Example delay distributions. Four example delay types defining the time spent by a cell in a given state. The plotted function, P(t) corresponds to the probability that after some time t, the cell remains in its current state, i.e., has not yet transitioned to the next state. In each example, is the median time of transition to the next state. While exponential-delays allow for instantaneous transitions (e.g., 10% of cells will have transitioned after 1.5 h has elapsed), the other three types enforce a minimum waiting period for almost all cells before transitioning from one state to the other (i.e., P(t) ≈ 1 for 0 < t < tmin). Enforcing this delay is more biologically realistic. The function P(t) appears explicitly in the viral infection model, Equation (1), and allows for generic delays between states of infection.