Africa is to be declared free from wild polio by the independent body, the Africa Regional Certification Commission.

Polio usually affects children under five, sometimes leading to irreversible paralysis. Death can occur when breathing muscles are affected by the paralysis.

There is no cure but the polio vaccine protects children for life.

The disease is now only found in Afghanistan and Pakistan

Nigeria is the last African country to be declared free from the disease, having accounted for more than half of all global cases less than a decade ago.

What is polio and has it now been eradicated in Africa?

Polio is a virus which spreads from person to person, usually through contaminated water. It can lead to paralysis by attacking the nervous system.

Two out of three strains of wild polio virus have been eradicated worldwide. On Tuesday, Africa is to be declared free of the last remaining strain of wild poliovirus.

More than 95% of Africa’s population has now been immunised. This was one of the conditions that the Africa Regional Certification Commission set before declaring the continent free from wild polio.

Now only the vaccine-derived polio virus remains in Africa.

This is a rare form of the virus that mutates from the oral polio vaccine and can then spread to under-immunised communities.

The World Health Organization (WHO) has identified a number of these cases in Nigeria, the Democratic Republic of the Congo, Central African Republic and Angola.

How did Africa eliminate wild polio?

Without a cure a vaccine developed in 1952 by Dr Jonas Salk gave hope that children could be protected from the disease. In 1961, Albert Sabin pioneered the oral polio vaccine which has been used in most national immunisation programmes around the world.

In 1996 poliovirus paralysed more than 75,000 children across the continent – every country was affected.

That year Nelson Mandela launched the “Kick Polio Out of Africa” programme, mobilising millions of health workers who went village-to-village to hand-deliver vaccines.

Since 1996 nine billion oral polio vaccines have been provided, averting an estimated 1.8 million cases of wild poliovirus.

What have the challenges been?

The last communities at risk of polio live in some of the most complicated places to deliver immunisation campaigns.

Nigeria is the last country in Africa to have reported a case of wild polio – in Borno state in Nigeria’s remote north-east, and the epicentre of the Boko Haram insurrection, in 2016.

At the time it was a frustrating set-back as the country had made huge progress and had gone two years without any cases being identified.

Outside Nigeria, the last place to have seen a case of polio was in the Puntland region of Somalia in 2014.

Conflict with the Islamist militant group Boko Haram has made parts of Nigeria particularly difficult to reach, Borno state in particular.