Final answer:
A disease outbreak is considered a density-dependent limiting factor because it becomes worse as the population density increases.
Step-by-step explanation:
A disease outbreak is considered a density-dependent limiting factor because it becomes worse as the population density increases. In other words, a higher population density increases the chances of the disease spreading and impacting a larger number of individuals. This is because diseases are often transmitted through close contact between individuals, and when there are more individuals in a given area, the likelihood of contact and disease transmission increases.