ISLAMABAD: Two cases of vaccine derived poliovirus have been reported from Punjab and Khyber Pakhtunkhwa (KP), taking the tally for the current year to 44.

According to an official of the National Institute of Health, requesting anonymity, an 18-month-old girl had been infected with the virus in Faisalabad district of Punjab.

“The other child from KP is also a female, resident of Lower Dir district. She is 15 months old,” he said.

“It is not wild polio virus outbreak. It is an outbreak of Sabin-Like Type 2 Derived (SLT2D) and same sort of outbreaks have been reported in a number of countries, including Philippines, China, Indonesia, Nigeria, Democratic Republic of Congo and several other countries in Africa which have completely eradicated the polio virus,” he said.

It is worth mentioning that there are three serotypes of wild poliovirus Type 1, Type 2, and Type 3 each with a slightly different capsid protein. Pakistan has been giving Type 1 and Type 3 viruses in Oral Polio Vaccines (OPVs) but had stopped administering Type 2 vaccine in years 2014 and virus could not be found even in environmental samples since 2016.

It is pertinent to mention that environmental sample is declared positive if virus is found in the sewage water.

“However, in 2019 suddenly cases reported from different areas which means there was some vial left in some laboratory or somewhere else and started spreading due to human error,” he said.

Published in Dawn, May 1st, 2020