What is a key difference in transmission potential between wild-type poliovirus and vaccine-derived poliovirus (VDPV)?

• A. Wild-type PV spreads via respiratory droplets.
• B. Both spread via fecal-oral routes; VDPV needs extended circulation in under-immunized populations to cause outbreaks.
• C. VDPV spreads only in vaccinated populations.
• D. Wild-type PV is not transmissible in under-immunized populations.

Answer: (B)

The main idea is how population immunity shapes transmission potential for poliovirus, especially the difference between wild-type and vaccine-derived strains. Poliovirus spreads mainly through the fecal-oral route, not by respiratory droplets, so transmission occurs when someone ingests material contaminated with infected feces, which is more likely in settings with poor sanitation.

Wild-type poliovirus can spread in any susceptible population and has the potential to cause outbreaks if immunity in the community is low. Vaccine-derived poliovirus, on the other hand, comes from the oral polio vaccine, which uses a live attenuated virus. In communities with insufficient immunity, this weakened virus can circulate for extended periods. During that time, it can accumulate mutations and regain neurovirulence, potentially causing outbreaks. However, this outbreak potential hinges on prolonged circulation in under-immunized populations; if immunity is high, transmission is quickly interrupted.

So the correct idea is that both forms spread via fecal-oral routes, but vaccine-derived poliovirus needs extended circulation in under-immunized populations to pose an outbreak risk.