The role of primary viremia in poliovirus pathogenesis is to allow the virus to do what?

• A. Trigger immediate neutralizing antibody production
• B. Spread from initial replication sites to the bloodstream
• C. Cross the blood-brain barrier directly
• D. Destroy motor neurons in the spinal cord

Answer: (B)

The main concept here is that the first viremia phase serves to move the virus from its initial replication sites into the bloodstream so it can disseminate systemically. After poliovirus replicates in the oropharynx and gut-associated lymphoid tissue, it enters the bloodstream, creating primary viremia. This step is what lets the virus reach distant organs, and if the immune system doesn’t clear it, the virus can reach the central nervous system during the subsequent phase (secondary viremia), where it may infect motor neurons and cause paralysis.

So, primary viremia’s role is to enable spread from the initial replication sites to the bloodstream, not to trigger immediate antibody production, not to cross the blood–brain barrier directly, and not to cause motor neuron destruction by itself. The motor neuron damage occurs later, once the virus has disseminated to the CNS during secondary viremia.