Where does poliovirus primarily multiply in the body?

• A. The liver
• B. The brain
• C. The intestines, particularly in lymphoid cells
• D. The lungs

Answer: (C)

Poliovirus multiplies primarily in the intestinal tract, especially within gut-associated lymphoid tissue such as Peyer’s patches. After ingestion, it replicates in the oropharynx and, more extensively, the intestinal mucosa and its lymphoid cells, leading to high viral loads shed in stool. This intestinal replication is why fecal-oral transmission is so efficient and why the gut is the main site of multiplication. In most cases the virus may spread systemically later, but the brain is not the initial or primary replication site; neuroinvasion, when it occurs, happens after hematogenous spread and affects motor neurons. The liver, lungs, and similar organs are not the primary sites where replication concentrates.