Explanation:

• Africa has been declared free from wild polio by the independent body, the Africa Regional Certification Commission.
• Now only the vaccine-derived polio virus remains in Africa.

When a country is certified as free of wild polio?

• A region is certified as free of wild polio after three years have passed without the virus being detected in any of its countries.
• Nigeria is the last African country to be declared free from wild polio.

Where wild polio is still present?

• Wild polio is still present in Pakistan and Afghanistan.

What is a vaccine-derived poliovirus?

• It is a strain of the weakened poliovirus that was initially included in oral polio vaccine (OPV)and that has changed over time and behaves more like the wild or naturally occurring virus.
• This means it can be spread more easily to people who are unvaccinated against polio and who come in contact with the stool or respiratory secretions, such as from a sneeze, of an infected person. These viruses may cause illness, including paralysis.

Hence all statements are correct.