Circulation and Molecular Epidemiology of Enteroviruses in Paralyzed, Immunodeficient and Healthy Individuals in Tunisia, a Country with a Polio-Free Status for Decades

Abstract

This report is an overview of enterovirus (EV) detection in Tunisian polio-suspected paralytic cases (acute flaccid paralysis (AFP) cases), healthy contacts and patients with primary immunodeficiencies (PID) during an 11-year period. A total of 2735 clinical samples were analyzed for EV isolation and type identification, according to the recommended protocols of the World Health Organization. Three poliovirus (PV) serotypes and 28 different nonpolio enteroviruses (NPEVs) were detected. The NPEV detection rate was 4.3%, 2.8% and 12.4% in AFP cases, healthy contacts and PID patients, respectively. The predominant species was EV-B, and the circulation of viruses from species EV-A was noted since 2011. All PVs detected were of Sabin origin. The PV detection rate was higher in PID patients compared to AFP cases and contacts (6.8%, 1.5% and 1.3% respectively). PV2 was not detected since 2015. Using nucleotide sequencing of the entire VP1 region, 61 strains were characterized as Sabin-like. Among them, six strains of types 1 and 3 PV were identified as pre-vaccine-derived polioviruses (VDPVs). Five type 2 PV, four strains belonging to type 1 PV and two strains belonging to type 3 PV, were classified as iVDPVs. The data presented provide a comprehensive picture of EVs circulating in Tunisia over an 11-year period, reveal changes in their epidemiology as compared to previous studies and highlight the need to set up a warning system to avoid unnoticed PVs.

Cases of Acute Flaccid Paralysis Associated with Coxsackievirus A2: Findings of a 20-Year Surveillance in the Russian Federation

“…Thus, the frequency of NPEV isolation from stool samples allows the assessment of the quality of surveillance for poliomyelitis and AFP. The frequency fluctuates in different countries depending on climatic and socio-economic conditions [14][15][16][17]. According to our data, in the Russian Federation, the proportion of AFP cases positive for NPEV was 3.2% in the period 2000-2019 (238 out of 7414).…”

“…Based on the goals of the poliomyelitis eradication program, the main objective of the surveillance is to detect poliovirus, and the main test materials are fecal samples [18]. However, owing to large sampling volumes and standardized methodology, there have been many scientific by-products of AFP surveillance, such as data on NPEV [14,17] and adenovirus circulation [57][58][59][60]. The future of AFP surveillance is currently debated, and some favor a more simple and versatile environmental surveillance program to trace both poliovirus and NPEV circulation.…”

“…The proportion of AFP cases from which non-polio enteroviruses (NPEV) were isolated varies from country to country: 4.3% in Tunisia [14], 6.12% in Poland [15], 19.4% in Italy [16], and 20.8% in the Philippines [17]. The etiological role of NPEV is not always obvious, since the WHO-recommended AFP case investigation algorithm consists of examining stool samples [18], and the isolation of ubiquitously present NPEV from a non-sterile specimen may be an accidental finding.…”

“…The detection of CVA2 virus from AFP cases is apparently a rare event [14,22,23], but in a study carried out in Brazil, CVA2 was one of the leading types of NPEVs isolated from AFP cases [24]. Among the 7280 AFP cases registered in the Russian Federation over 20 years (2001-2020) [25], CVA2 was isolated from only five cases.…”

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

“…All isolates were classified as Sabin-like strains according to the WHO definition (≤ 9 nucleotide substitutions for type 3). One isolate collected in January 2019 had seven substitutions (0.78%) and was characterised according to the classification used previously by other authors [ 13 ] as high-mutant strain pre-VDPV (between six and nine nucleotide sequence variations). The low extent of sequence divergence suggests that these viruses were probably associated with a recent vaccination event.…”