We Might Expect Virulence of a Particular Human Pathogen to Decrease

Question

We might expect virulence of a particular human pathogen to decrease:
A) when opportunities for transmission are limited.
B) when opportunities for transmission are abundant.
C) when animal reservoirs for the pathogen are scarce.
D) in very large human populations, such as a large city.
E) when it uses insect vectors for transmission.

Accepted Answer

When opportunities for transmission are limited, the pathogen cannot spread as easily, and so it may decrease its virulence to avoid killing its host too quickly and reducing its own chances of transmission. This is known as the "trade-off hypothesis" of virulence.