Polio reached Malawi from Pakistan, six years after Africa was declared free of it

**Endemic transmission of wild poliovirus type 1 continues only in Afghanistan
and Pakistan.** That sentence has been true for years, and it is easy to read
as containment.

In **2022, Malawi and Mozambique reported wild poliovirus type 1 cases linked
to a Pakistan strain** — the first in the African region since 2016.

Why that is the important fact

The African region had been certified free of indigenous wild poliovirus. The
virus did not re-emerge there; it travelled, several thousand kilometres,
and found populations where immunity had fallen far enough for it to take hold.

Afghanistan and Pakistan also reported cases during 2022 and 2023, and
**circulating vaccine-derived polioviruses were detected in areas of the world
where poliovirus had been eliminated.** In **multiple countries, more than one
poliovirus type was circulating at the same time.**

So there are now two ways for polio to appear somewhere it had gone: imported
wild virus, and vaccine-derived virus emerging locally. Both need the same
condition.

The conclusion, which is about everywhere else

**The detections of poliovirus in areas where it had been previously
eliminated underscore the threat of continued poliovirus spread to any area
where the population is insufficiently vaccinated against poliovirus.**

Any area. Eradication is not a race that two countries are losing while the
rest have won. Until transmission stops everywhere, every country's freedom
from polio is held in place by its own vaccination coverage — and coverage is
the one thing that erodes quietly, without producing a single case, until a
traveller arrives.

Which is what Malawi's 2022 case demonstrates: not a failure of the eradication
campaign in Pakistan alone, but what happens when a gap opens anywhere and the
virus is still in the world.

Source: Centers for Disease Control and Prevention, MMWR.