#NewsBytesExplainer: Is discovery of poliovirus in Kolkata cause for worry?
What's the story
Amid reports of the resurgence of the poliovirus, a pathogen responsible for poliomyelitis (polio), in Kolkata, health experts have dispelled the fear and rubbished claims. Notably, the World Health Organization (WHO) declared India polio-free on March 27, 2014. Therefore, the detection of traces of poliovirus caused considerable alarm among the people. However, experts said that it wasn't a cause for concern. Here's more.
Infection
Poliovirus detected in Metiabruz was 'vaccine virus' not 'wild virus'
A West Bengal Health Department official said that the poliovirus found in the sewage in the Kolkata's Metiabruz area was a "vaccine virus" and not a "wild virus." Unlike a "wild virus," a "vaccine virus" is not capable of infecting anyone. WB reported its last polio case in 2011 when a two-year-old girl in the Howrah district was found to have contracted the disease.
Reasons
Possible reasons for finding virus in sewage
West Bengal Director of Health Services (DHS) Dr. Siddhartha Niyogi said that the possibility of finding the virus in sewage could be that the virus might have been excreted by a child who received the live polio vaccine. Another reason could be open defecation by the child. The virus detected in the sewage is reportedly a vaccine-derived poliovirus (VDPV Type 1), an official said.
Genetic sequencing
Pune's NIV found virus to be inactive
According to a report by PTI, Pune's National Institute of Virology had done genetic sequencing of the traces and found the virus to be inactive. It also quoted health ministry officials as saying that the poliovirus which was detected in the environmental surveillance of sewage was vaccine-derived and not the wild poliovirus. VDPV Type 1 was reportedly last detected in New Delhi in 2018.
About
What is poliomyelitis?
Polio is a highly infectious viral disease that largely affects children under five years of age. The virus is transmitted by person-to-person spread mainly through the fecal-oral route. Sometimes, it is also transmitted by contaminated water or food. The virus multiplies in the intestines and then affects the nervous system and the spinal cord and can cause paralysis.
Three types
Types of wild poliovirus
According to the US Centers for Disease Control and Prevention, there are three wild types of poliovirus. While Types 2 and 3 have been eradicated, Type 1 still remains. Type 2 was declared eradicated in September 2015, with the last virus detected in India in 1999. Type 3 was declared eradicated in October 2019. As of 2020, Type 1 affects two countries—Pakistan and Afghanistan.
Usage
Types of polio vaccines
There are two types of vaccines for protection from polio: inactivated poliovirus vaccine (IPV) and oral poliovirus vaccine (OPV). IPV is the only polio vaccine used in the US since 2000 as the OPV is not licensed there. The OPV is administered to children in many parts of the world, including India. Children receive doses of the vaccine by drops in the mouth.