With the reports of an additional three cases of circulating vaccine-derived poliovirus type 1 (cVDPV1), this brings the total cases to eight in 2015 in Madagascar.

Poliovirus  Image/CDC
Poliovirus Image/CDC

The Global Polio Eradication Initiative (GPEI) says the most recent case had onset of paralysis on 29 May in Boeni region. These cases are genetically linked to a case reported in September 2014, indicating prolonged and widespread circulation of the virus.

What are Vaccine-derived polioviruses (VDPVs)?

The GPEI defines it as follows:

The oral polio vaccine contains a live, attenuated (weakened) vaccine-virus. When a child is vaccinated, the weakened vaccine-virus replicates in the intestine and enters into the bloodstream, triggering a protective immune response in the child. Like wild poliovirus, the child excretes the vaccine-virus for a period of six to eight weeks. Importantly, as it is excreted, some of the vaccine-virus may no longer be thesame as the original vaccine-virus as it has genetically altered during replication. This is called a vaccine-derived poliovirus.

In other polio news, one new wild poliovirus type 1 (WPV1) case was reported in the past week in Quetta district, Balochistan province, Pakistan. The total number of WPV1 cases in Pakistan for 2015 is now 26, compared to 83 at this time last year.

Globally, only 30 cases have been reported (4 cases from Afghanistan), compared to 114 during the same period in 2014.

In Nigeria, it has been a year since the African country has reported a case of polio (The most recent case had onset of paralysis on 24 July 2014).