Which of the following infectious agents has evolved to maintain a persistent state in its host?

• A. Herpes simplex virus
• B. Influenza virus
• C. Norovirus
• D. Streptococcus pyogenes

Answer: (A)

Verified step by step guidance

1. Understand the concept of a persistent infection: This occurs when an infectious agent remains in the host for a long period, often by evading the immune system, sometimes with periods of latency and reactivation.
2. Review the characteristics of each infectious agent listed: Herpes simplex virus, Influenza virus, Norovirus, and Streptococcus pyogenes.
3. Recall that Herpes simplex virus is known for establishing latency in nerve cells, allowing it to persist in the host and reactivate later, causing recurrent infections.
4. Contrast this with Influenza virus and Norovirus, which typically cause acute infections that are cleared by the immune system without long-term persistence.
5. Note that Streptococcus pyogenes is a bacterium that usually causes acute infections and does not maintain a persistent latent state like Herpes simplex virus.