Poliovirus figures i

• • • 95% : asymptomatic (primary viremia): develop neutralizing Ab which prevent or terminate viremia.
    • 5% : delayed immune repsonses (secondary viremia): flu-like symptoms, mostly immune defences terminate the viremia, after 2 D (abortive polio)
    • <1% : aseptic meningitis : virus crosses blood brain barrier (or to CNS via nerve fibers), self limited.
    • 0.1%: CNS involvement (motor neurons in spinal cord, medulla or cerebral cortex) : Via hematogenous route or indirectly when virus infects peripheral sensory ganglia and is transported intra-axonally to CNS. 1/200 is permantent paralyses