Final answer:
A virus can cause different reactions amongst the host, with factors like host immunity and virus strain playing roles. Viruses like HIV and influenza affect hosts differently, with genetic variability contributing to these reactions. For a new virus to emerge, it must find a suitable host and be able to effectively replicate and spread.
Step-by-step explanation:
The correct answer to whether a virus can cause different reactions amongst the host is True. Viruses can indeed evoke a range of responses depending on a host of factors including but not limited to the host's genetic makeup, immune system strength, and the specific characteristics of the virus itself. For example, the HIV virus affects host genetic variability by integrating itself into the host genome and can remain latent for long periods. In contrast, the influenza A virus has a rapid replication cycle, causing immediate and sometimes severe symptoms.
Different strains of a virus can also produce varied responses due to the genetic variation that arises during replication. Moreover, the interaction between viral proteins and cell-surface receptors is critical to infection and its outcomes. Changes in these proteins can lead to new virus types capable of infecting new hosts, potentially leading to the emergence of new epidemics. Close contact environments, like farms, provide opportunities for this to happen.
An essential prerequisite for a new virus to emerge and spread is the existence of a suitable host with compatible cell-surface receptors for the virus to bind to. Additionally, the virus must overcome the host's immune response and be able to replicate effectively to spread among the population.