HIV at one time only infected nonhuman primates but now infects humans as well. Likewise, the avian flu only infected birds but now infects humans. What causes the host range of a virus to increase?

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Quizplus · Accepted Answer

Viruses can evolve through random mutations and changes in their genome, which can allow them to gain entry into new host cells. This can lead to an expansion of their host range, as seen with the transmission of certain viruses from nonhuman primates to humans or from birds to humans. Other factors, such as changes in human or animal genomes, may also contribute to increased susceptibility to certain viruses, but these are not the primary cause of host range expansion.

HIV at One Time Only Infected Nonhuman Primates but Now