The respiratory route of transmission of virulent polioviruses.

AIMS: The route of transmission of wild and circulating vaccine-derived polioviruses remains controversial, between respiratory and faecal-oral, and we aim to identify the most plausible one to settle the controversy.

METHODS

We explored available epidemiological clues and evidence in support of either route in order to arrive at an evidence-based conclusion.

RESULTS

Historically the original concept was respiratory transmission based on epidemiological features of age distribution, which was later revised to faecal-oral as the rationale for popularising the live attenuated oral polio vaccine in preference to the inactivated poliovirus vaccine. Through epidemiological logic, we find no evidence for the faecal-oral route from available studies and observations, but all available information supports the respiratory route.

CONCLUSIONS

The route is respiratory, not faecal-oral. The global polio eradication initiative assumed it was faecal-oral - and its gargantuan efforts based on this assumption have failed in two ways: eradication remains pending and circulating vaccine-derived polioviruses have seeded widely. With clarity on the route of transmission the choice of vaccine is also clear - it can only be the inactivated poliovirus vaccine.