196. Latency is a characteristic of which one of the following viruses?
A. Herpes virus
B. Polio virus
C. Rhino virus
D. Influenza virus

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Explanation:

Latency refers to a phase in the viral life cycle where the virus remains dormant within the host after the initial infection. During latency, the virus is not actively replicating, and the host does not show symptoms of the infection. The virus can reactivate later, causing recurrent infections.

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Why Herpes Virus?

Herpes viruses, such as Herpes Simplex Virus (HSV) and Varicella-Zoster Virus (VZV), are known for their ability to establish latent infections. The key features of latency in herpes viruses are:

• Nervous system involvement: Herpes viruses often enter a dormant phase in nerve cells (neurons) after the primary infection.

• Reactivation triggers: Latency can be triggered by factors like stress, immune suppression, or other environmental changes.

• Recurrent outbreaks: After reactivation, the virus can cause recurrent outbreaks (e.g., cold sores or shingles).

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 Why Not the Other Viruses?

• Polio virus: Polio does not establish latency. It causes acute infection and is typically cleared by the immune system.

• Rhinovirus: This virus, responsible for the common cold, does not exhibit latency. It causes acute, self-limiting infections.

• Influenza virus: Influenza does not establish latency. It leads to seasonal flu outbreaks but does not remain dormant in the host.

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Conclusion:

Herpes viruses are unique in their ability to enter a latent state, reactivating later and causing recurrent infections, which makes latency a hallmark of these viruses.