Re-emergence of poliovirus in French Guiana: An alert for the Americas

Poliovirus, once eradicated from French Guiana, has re-emerged recently.This marks the first detection of circulating vaccine-derived poliovirus type 3 (cVDPV3) in the region since 1983 when French Guiana was declared polio-free [1,2].The virus was identified in a wastewater sample collected on 26 June 2024 in Cayenne as part of a research project by the French research agency for emerging infectious diseases (ANRS-MIE).On 2nd August 2024, the Global Specialized Lab (GSL) of the Global Polio Lab Network (GPLN) at the Institut Pasteur in Paris notified Sant Publique France and other French health authorities of the VDPV3 detection [1].Poliovirus belongs to the enterovirus genus in the Picornaviridae family.It is a small, non-enveloped virus with a single-stranded positive RNA, resistant to acidic conditions.Wild poliovirus (WPV) has 3 serotypes -WPV1, WPV2 and WPV3 distinguished by a slightly different capsid protein [3].VDPVs can emerge when oral polio vaccine (OPV) viruses proliferate in populations with low herd immunity (cVDPVs) or when they persist in immunocompromised individuals (iVDPVs).Through genetic changes such as recombination with other enteroviruses or reversion of OPV strains, these VDPVs can regain the neurovirulence and transmissibility of WPV.This genetic divergence from the attenuated OPV indicates prolonged replication and circulation, raising significant public health concerns [3,4].The recent detection of cVDPV3 in French Guiana, which exhibits 15 mutations in the poliovirus protein 1 (VP1), highlights this threat.These mutations represent a significant genetic divergence from previously identified strains, enhancing the virulence and lead to paralysis, particularly in populations with insufficient immunisation [1].Polio is highly infectious and transmitted mainly through the faecaloral route.After entry, the virus replicates in the lymphatic tissues of the oropharynx and gut, causing asymptomatic viremia, followed by spread to the reticuloendothelial system [3].In rare cases poliovirus crosses the blood brain barrier or travels via peripheral nerves to the central nervous system, causing non paralytic aseptic meningitis in up to 5 % of infections depending on the virus type and the invasion site [3] (Fig. 1.).Poliovirus infections are mainly asymptomatic, however, 1-2% may