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The vaccine-derived polio virus was detected during environmental monitoring of sewage samples from Kolkata, a health ministry official said.

The vaccine-derived polio virus was detected during environmental monitoring of sewage samples from Kolkata, a health ministry official said.

It was not wild poliovirus but vaccine-derived poliovirus (VDPV) that was detected during environmental monitoring of sewage samples from Kolkata, a senior health ministry official said on Thursday. “Genetic sequencing is being done at the ICMR-National Institute of Virology in Mumbai, and this has been discussed with the World Health Organization (WHO). It can occur in any country where oral polio vaccine (OPV) is administered,” the official added.

The ministry said the last time such a VDPV was detected was in New Delhi in 2018.

State health officials detected the presence of VDPV in sewage in Kolkata earlier this week. A VDPV is a weakened poliovirus strain that was originally included in OPV and has changed over time to behave more like the wild or natural virus.

Kolkata officials added that sewage monitoring continues across the country and that this virus was found in a sample in Kolkata. “Most likely it came from the gut of an immunocompromised person and has since multiplied. This is not a case of human-to-human polio transmission,” state health officials said.

According to the WHO, poliomyelitis (poliomyelitis) is a highly contagious viral disease that largely affects children under the age of five. The virus is transmitted from person to person mainly by the fecal-oral route or, less frequently, by a common vehicle (for example, 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 cases of wild poliovirus type 3 have been discovered since the last reported case in Nigeria in November 2012. Both strains have been officially certified as globally eradicated. As in 2020, wild poliovirus type 1 affects two countries, Pakistan and Afghanistan, according to the WHO.