Why is it more difficult to develop antiviral drugs than anti-infectives?

The development of antiviral drugs is more challenging compared to anti-infective agents, primarily because viruses are tiny and replicate inside host cells. This intracellular replication presents a significant hurdle for drug development.

When a virus infects a host cell, it hijacks the cellular machinery to replicate and produce new viral particles. This process occurs within the host cell's environment, which makes it difficult to target the virus without also affecting the host's cells. The drugs need to selectively inhibit viral replication while minimizing harm to the host's normal cellular functions.

Additionally, because viruses rely on host cell processes for replication, any antiviral agent must be designed to interfere specifically with viral functions or processes that are distinct from those of the host cell, which is a complex task.

This intracellular lifestyle also allows for easier mutation and evolution of viruses, resulting in the emergence of resistant strains, further complicating antiviral drug development. Thus, the nature of viral replication makes targeting them with drugs more complicated compared to targeting bacteria or other pathogens that do not rely on host cellular mechanisms in the same way.