What are viral infections characterized by?

Viral infections are characterized by small entities that invade healthy body cells. Viruses are much smaller than bacteria and cannot be seen without a microscope. They require a host cell to replicate and carry out their life cycle, which often involves taking over the cellular machinery of the host to produce more viral particles. When a virus infects a cell, it can disrupt normal cellular function and lead to various symptoms and diseases.

The other options do not accurately describe viral infections. They either mischaracterize the size and nature of viruses or incorrectly attribute the types of pathogens responsible for infections. Understanding the specific characteristics of viral infections is crucial in recognizing how they differ from bacterial infections and how they interact with the human body.