Not wild poliovirus but vaccine-derived poliovirus (VDPV) was detected in the environmental surveillance of sewage samples from Kolkata, said a senior Health Ministry official on Thursday. “The genetic sequencing is done at ICMR-National Institute of Virology, Mumbai, and this was discussed with the World Health Organisation (WHO). It can occur in any country where oral polio vaccine (OPV) is given,’’ added the official.
The Ministry said that the last time such a VDPV was detected was in New Delhi in 2018.
State health officials detected the presence of VDPV from sewage waters in Kolkata earlier this week. A VDPV is a strain of the weakened poliovirus that was initially included in OPV and that has changed over time and behaves more like the wild or naturally occurring virus.
Officials from Kolkata added that sewage monitoring goes on throughout the country and this virus was found in a sample in Kolkata. “Most likely it has come from someone’s gut who is immune deficient and has since multiplied. It is not a case of human-to-human polio transfer,” said State health authorities.
According to WHO, Poliomyelitis (polio) is a highly infectious viral disease that largely affects children under five years. The virus is transmitted by person-to-person spread mainly through the faecal-oral route or, less frequently, by a common vehicle (e.g. contaminated water or food) and multiplies in the intestine, from where it can invade the nervous system and cause paralysis.
Of the three strains of wild poliovirus (type 1, type 2 and type 3), wild poliovirus type 2 was eradicated in 1999 and no case of wild poliovirus type 3 has been found since the last reported case in Nigeria in November 2012. Both strains have officially been certified as globally eradicated. As on 2020, wild poliovirus type 1 affects two countries — Pakistan and Afghanistan — according to the WHO.
