Final answer:
A person with a viral infection can be contagious before showing symptoms due to the replication process of viruses. In this process, viruses create new virus particles within the host's body that could be shed and transmitted even before the host shows any signs of illness. A clear example of this can be seen in latent viral infections.
Step-by-step explanation:
A person with a viral infection can be contagious before they start showing symptoms due to the way viruses replicate inside the host's body. The process of viral replication involves several steps: attachment, penetration, uncoating, replication, assembly, and release.
During these stages, the virus uses the host cell's machinery to reproduce, creating new virions, or virus particles. This can happen before the host's immune system recognizes the infection and triggers symptoms. Thus, without showing signs of illness, the individual can already be shedding new virions, making them contagious.
A significant example of this is seen in latent infections, where some types of viruses, known as latent viruses, can initially cause an acute infection before becoming dormant. Despite the 'silence' period of these viruses, they can still be transmitted to other individuals, further spreading the infection without immediate recognition.
Learn more about Viral Infection and Contagiousness