Environmental monitoring of wastewater in Jerusalem, Israel, has detected an increasing population of poliovirus type 2. Additionally, these viral isolates are associated with vaccine-derived viral strains. A detailed report has recently been published in Eurosurveillance, the European journal on surveillance, epidemiology, prevention and control of infectious diseases.
Rapid Communication: Emergence of genetically linked vaccine-derived poliovirus type 2 in the absence of oral polio vaccine, Jerusalem, April-July 2022. Image credit: Kateryna Kon/Shutterstock
background
Environmental surveillance programs aim to detect circulating pathogens in different sources involved in pathogen transmission. The most commonly used sources are wastewater, wastewater, drinking water, air, and fomites. These programs are especially necessary to monitor the abundance of clinically undetected pathogens and their potential to cause public health risks.
Israel’s environmental monitoring program covers 15 regions across the country, including 50% of the general population. In addition, Jerusalem has four non-overlapping surveillance regions.
Detection and genomic analysis of poliovirus type 2
Additional wastewater surveillance programs have increased surveillance of poliovirus-related acute flaccid paralysis in Israel since 1989. The presence of poliovirus type 2 has been detected in two regions of Jerusalem and one region of central Israel in April 2022.
As of July 2022, the number of detections of poliovirus type 2 in sewage has been found to increase significantly in the Jerusalem regions. In addition, genomic sequencing of viral isolates has demonstrated the accumulation of mutations over time.
In three different regions of Jerusalem, two isolates of poliovirus type 2 have been detected over a 100-day period. Sequencing analysis has revealed that these isolates are associated with vaccine-derived poliovirus.
Five additional isolates of poliovirus type 2 have been detected during the same period; however, these isolates are unrelated to the vaccine-derived viral strain. Poliovirus type 2 sequences isolated in 2022 were found to share a 2-nucleotide signature in the VP1 gene. This gene encodes the major protein of the viral capsid VP1.
To further identify the genetic link between the isolates, whole genome sequencing has been carried out for the isolates collected between 2020 and 2022. The findings have shown the presence of additional mutations in the P1 genomic region in all the sequences isolated in 2022. The P1 region includes VP1. genes , VP2, VP3 and VP4. However, these shared mutations were not present in the sequences isolated in 2020 and 2021.
Considering the P2/3 genomic region, recombination with a non-polio enterovirus has been detected in the 3A gene. However, this recombination was absent in all poliovirus sequences isolated in 2020 and 2021.
Overall, these observations strongly identify genetic linkage between all poliovirus type 2 sequences isolated in 2022.
Study the importance
Environmental surveillance in Israel has detected an increasing frequency of poliovirus type 2 isolates in different regions of Jerusalem. These isolates are genetically associated with the vaccine-derived strain of poliovirus type 2.
Vaccine-derived polioviruses originate primarily from genetically mutated oral poliovirus vaccine strains that accumulate mutations over time. A high rate of viral transmission in populations with low immunity, or a high rate of viral replication in immunocompromised patients, is responsible for the origin of vaccine-derived polioviruses.
Oral poliovirus type 2 vaccination was discontinued globally in April 2016 due to outbreaks of vaccine-derived poliovirus type 2. Therefore, monovalent oral poliovirus type 2 vaccination has been introduced as a preventive measure to control these outbreaks.
As of July 2022. Only localized transmission of poliovirus type 2 has been detected in Jerusalem. To date, no incidence of virus-induced acute flaccid paralysis has been observed. To control these outbreaks, the Israeli Ministry of Health has decided to immunize children with inactivated poliovirus vaccines.
Overall, the study highlights the importance of routine environmental surveillance to quickly identify outbreaks caused by vaccine-derived polioviruses and control outbreaks through rapid vaccination campaigns.