New study in Nature Microbiology on the spatiotemporal heterogeneities of wild and vaccine-derived poliovirus

Published on November 27, 2025, by Simon Dellicour

Outbreaks of vaccine-derived poliovirus type 2 (cVDPV2) have become a major threat to polio eradication. In this new study just published in Nature Mircobiology and condcted in collabotion with the Imperial College and the WHO, we analyse cVDPV2 cases and Wild-type poliovirus 1 (WPV1) sequences to uncover the spatiotemporal patterns and drivers of poliovirus spread. Between May 1, 2016 and September 29, 2023, 3120 cVDPV2 cases were reported across 76 outbreaks and 39 countries globally. Outbreaks have mostly been small (median = 5 cases, range 1-578), have spread to a median maximum distance of 231 km (0-4442) and for median duration of 202 days (0-1905). Wavefront velocity analysis of large outbreaks reveals a median velocity of spread of 2.3 km/day (1.0-4.4). International borders are associated with a slower velocity of spread (p < 0.001), when in the presence of high population immunity. Finally, phylogeographic analysis of 1572 global sequences, including 38 newly generated (1953-2015), reveals that historic WPV1 spread resembles recent cVDPV2 patterns and that international spread is largely sustained by unidirectional movement between neighbouring countries. Our findings offer insights for enhancing the geographical scope of poliovirus surveillance and response, crucial steps in the final phases of poliovirus eradication. Read the whole study here.

From a methodological perspective, this study has been the opportunity to apply an analytical framework that we previously implemented — in the context of the African Swine virus outbreak in Wallonia, Belgium (2018-19) — to study the dynamic of wavefront progressions and the environmental factors impacting it (Dellicour et al. 2020). The R script developed to conduct these analyses is available on a dedicated GitHub repository.

(Adapted from) Figure S12: illustration of the wavefront velocity analysis workflow using the the NIE-ZAS-1 VDPV outbreak as an example. (1) Invasion times (days) for all cVDPV2 AFP cases reported. Invasion times were calculated as the difference in days between the onset of each case and the first case of the outbreak (origin). (2) First invasion times for filtered cases only. Cases were filtered to include only those extending the wavefront of the outbreak (see methods). (3) Interpolation of invasion times for filtered cases on the raster surface. (4) Estimation of friction (time/distance) based on the interpolated invasion times for filtered cases. Outbreak wavefront velocity was estimated as the inverse of the friction (not shown, see Methods for details).

Reference: Candido DS, Dellicour S, Cooper L, Prete CA, Jorgensen D, Uzzell C, Voorman A, Lyons H, Klapsa D, Majumdar M, Arowolo K, Peak C, Bandyopadhyay A, Martin J, Grassly N, Blake I (2025). Unravelling spatiotemporal heterogeneities of wild and vaccine-derived poliovirus spread: past and present. Nature Microbiology, in press