Isolation of Sabin-like Polioviruses from Sewage in Poland

Investigation of airport sewage to detect importation of poliovirus, Poland, 2017 to 2020

BackgroundPolioviruses are human pathogens which may easily be imported via travellers from endemic areas and countries where oral polio vaccine (OPV) is still routinely used to polio-free countries. Risk of reintroduction strictly depends on polio immunisation coverage. Sustaining a polio-free status requires strategies that allow rapid detection and control of potential poliovirus reintroductions.AimThe aim of this study was to apply environmental surveillance at an international airport in Poland to estimate the probability of poliovirus importation via air transport.MethodsBetween 2017 and 2020, we collected 142 sewage samples at Warsaw Airport. After sewage concentration, virus was isolated in susceptible cell cultures. Poliovirus isolates were characterised by intratypic differentiation and sequencing.ResultsSeven samples were positive for polioviruses. All isolates were characterised as Sabin-like polioviruses type 3 (SL-3). No wild or vaccine-derived polioviruses were found. The number of mutations accumulated in most isolates suggested a limited circulation in humans. Only one SL-3 isolate contained seven mutations, which is compatible with more than half a year of circulation.ConclusionSince OPV was withdrawn from the immunisation schedule in Poland in 2016, detection of SL-3 in airport sewage may indicate the events of importation from a region where OPV is still in use. Our study shows that environmental surveillance, including airport sewage investigation, has the capacity to detect emerging polioviruses and monitor potential exposure to poliovirus importation. Poliovirus detection in sewage samples indicates the need for sustaining a high level of polio immunisation coverage in the population.

Environmental Surveillance of Polioviruses in Armenia, Colombia before Trivalent Oral Polio Vaccine Cessation

Although acute flaccid paralysis (AFP) surveillance is the "gold standard" for detecting cases of polio, environmental surveillance can provide supplementary information in the absence of paralytic poliomyelitis cases. This study aimed to detect the introduction and/or circulation of wild poliovirus or vaccine-derived polioviruses (VDPV) in wastewater, covering a significant population of Armenia, Colombia, before trivalent oral polio vaccine (OPV) cessation. Between March and September 2015, 24 wastewater samples were collected from eight study sites in eight communes of Armenia, Colombia. Virus detection and characterization were performed using both cell culture (i.e., RD or L20B cells) and RT-PCR. Polioviruses were isolated in 11 (45.8%) of 24 wastewater samples. All isolates were identified as Sabin strains (type 1 = 9, type 3 = 2) by intratypic differentiation. Type 2 poliovirus was not detected in any of the samples. No wild poliovirus or VDPV was detected among the isolates. Non-polio enterovirus was identified in 8.3% (2/24) of the samples. This study revealed the excretion of Sabin poliovirus from OPV-immunized individuals, as well as the absence of VDPV and wild poliovirus in wastewaters of Armenia, Colombia. This confirms that environmental surveillance is an effective method, as an additional support to AFP surveillance, to monitor poliovirus during the OPV-to-IPV (inactivated polio vaccine) transition period.