A Human Population Is Struck Down by a Viral Epidemic

A human population is struck down by a viral epidemic resulting in a high percentage of mortality. Virologist one argues that this is most likely due to the virus having mutated, while virologist two contends that the virus has switched hosts. Which virologist is most likely to be correct and why?

A) Virologist A, even though viruses have low rates of mutation due to error checking polymerase enzymes.
B) Virologist B, as host switching occurs commonly in nature.
C) Both hypotheses are probably wrong, as neither mutation nor host switching is likely to result in a virulent outbreak.
D) Virologist A, as host switching is always associated with a wild population and a human population.
E) Both hypotheses are equally plausible as both mutation and host switching can result in virulent outbreaks.