Question

Which of the following types of viruses would you expect to require periods of latency? a. viruses that have large genomes and require a long time for replication b. viruses that require a long time for transmission to new hosts c. viruses that require a long time for assembly into complex structures d. viruses that infect cells of the immune system

Short answer

The viruses that would require periods of latency are: b. viruses that require a long time for transmission to new hosts d. viruses that infect cells of the immune system

Step-by-step solution

Option A: Large genomes and require a long time for replication

A virus with a large genome might take more time to replicate, but this doesn't necessarily mean it requires a period of latency. Latency is related to the virus's ability to be inactive and hidden from the immune system, not just the time it takes to replicate.

Option B: Require a long time for transmission to new hosts

A virus that requires a long time for transmission to new hosts might benefit from a period of latency because it allows the virus to stay in the current host without causing symptoms, making it more likely to be transmitted to a new host.

Option C: Require a long time for assembly into complex structures

A virus that requires a long time for assembly into complex structures may take longer to cause symptoms in the host, but this doesn't directly relate to latency. Again, latency is about the virus being inactive and hidden from the immune system.

Option D: Infect cells of the immune system

A virus that infects cells of the immune system could benefit from periods of latency, as it would allow the virus to remain hidden within the very system that is meant to detect and eliminate it. This strategy would make it more likely for the virus to survive and potentially spread to new hosts. Based on our analysis of each option, the correct answer is: b. viruses that require a long time for transmission to new hosts d. viruses that infect cells of the immune system

Key concepts

Viral Replication

Understanding how viruses multiple is crucial for grasping why some viruses require periods of latency. Viral replication is the process by which viruses produce new particles. It begins when a virus attaches itself to a host cell and injects its genetic material into it. The virus then hijacks the cell's machinery to transcribe and replicate its genome and to synthesize viral proteins. These components are assembled into new viral particles, which are then released to infect more cells.

Despite this seemingly straightforward process, latency can play a crucial role. Some viruses, after initial replication, enter a dormant state where they do not produce new viruses. This can happen for several reasons, such as evasion of the host's immune response or waiting for favorable conditions to resume replication. Latency allows these viruses to persist unnoticed, potentially reactivating under specific triggers like stress or immune suppression. Exploring viral replication further, one would discover various replication strategies among different viruses, some being rapid and aggressive while others are slower and more prone to entering latency.

Immune System Infection

Infections that involve the immune system can be particularly insidious due to the role the immune system plays in fighting pathogens. When a virus infects cells of the immune system, it's attacking the very entity that's supposed to protect the body against it. HIV is a well-known example of such a virus. By targeting immune cells, specifically T-helper cells, it depletes the body's defensive capabilities.

This self-attacking mechanism can be a reason for a virus to go latent. As the immune system is compromised, the virus hides within the cells it's designed to destroy. During latency, the virus is not recognized by the immune system and thus is not attacked, allowing it to persist for an extended period. This survival tactic is a fascinating yet disturbing phenomenon because it allows the virus to stay in the body for a long time, sometimes even for the life span of the host, without being cleared, thereby increasing the chances of transmission and complicating treatment efforts.

Transmission of Viruses

The spread of viruses from one host to another, referred to as transmission of viruses, is a key factor in the survival and proliferation of a virus. Some viruses can transmit easily and rapidly, such as those causing the common cold, while others take more time to find a new host. Viruses that require close contact or specific transmission vectors may stay dormant in a host during periods where transmission opportunities are low.

The period of latency can thus be seen as a survival strategy during unfavorable conditions for transmission. By not causing symptoms, the virus avoids drawing attention to itself, which might result in the host being isolated or treated, reducing the chance of transmission. Understanding the dynamics of viral transmission helps in developing preventive strategies, such as targeted vaccinations or public health policies aiming at breaking the chain of transmission and containing viral outbreaks.