Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Phylogeographical and Evolutionary History of Variola major Virus; A Question of Timescales?

Version 1 : Received: 11 December 2020 / Approved: 14 December 2020 / Online: 14 December 2020 (09:21:34 CET)

How to cite: Bergna, A.; Della Ventura, C.; Marzo, R.; Ciccozzi, M.; Galli, M.; Zehender, G.; Lai, A. Phylogeographical and Evolutionary History of Variola major Virus; A Question of Timescales?. Preprints 2020, 2020120310 (doi: 10.20944/preprints202012.0310.v1). Bergna, A.; Della Ventura, C.; Marzo, R.; Ciccozzi, M.; Galli, M.; Zehender, G.; Lai, A. Phylogeographical and Evolutionary History of Variola major Virus; A Question of Timescales?. Preprints 2020, 2020120310 (doi: 10.20944/preprints202012.0310.v1).

Abstract

In order to reconstruct the origin and pathways of variola virus (VARV) dispersion, we analyzed 47 VARV isolates available in public databases and their SNPs. The mean substitution rate of the whole genomes was 9.41x10-6 (95%HPD:8.5-11.3x10-6) substitutions/site/year. The time of the tree root was estimated to be a mean 68 years (95%HPD:60.5–75.9). The phylogeographical analysis showed that the Far East and India were the most probable locations of the tree root and of the inner nodes, respectively, whereas for the outer nodes it corresponded to the sampling locations. The Bayesian Skyline plot showed that the effective number of infections started to grow exponentially in 1915-1920, peaked in the 1940s, and then decreased to zero. Our results suggests that the VARV major strains circulating between 1940s-1970s probably shared a common ancestor originated in the Far East; subsequently moved to India, which became the center of its dispersion to eastern and southern Africa, and then to central Africa and the Middle East, probably following the movements of people between south-eastern Asia and the other places with a common colonial history. These findings may help to explain the controversial reconstructions of the history of VARV obtained using long- and short- term calibrations.

Subject Areas

Variola major; phylogeographical analysis; long-term calibrations; short- term calibrations

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