Our new preprint on clade I MPXV (co-led by Akira Endo, Toshiaki Asakura and myself) is out! Using mathematical models accounting for age- and sex-dependent contact patterns, we estimated the relative roles of community and sexual contacts in clade I transmission dynamics.

🔗 https://doi.org/10.1101/2024.10.15.24315554

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@Toshiaki_R_A
Borame L Dickens
Jen Han Foo
Shihui Jin
Patrick K Mukadi
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@kiesha_prem
@_akiraendo

Summary

Clade Ia MPXV has historically circulated in DRC mainly through animal exposure followed by limited human-to-human transmission. In contrast, the rapid spread of clade Ib in South Kivu, DRC suggested sustained human-to-human transmission.

Although initial investigation of the clade Ib outbreak found heterosexual contacts among female sex workers (FSWs) and their clients as key exposure routes, general community contacts may also play a role, with children accounting for a significant proportion of reported cases.

To assess the relative contribution of community and sexual contact transmission, we modelled age- and sex-dependent contact patterns to explain the observed age/sex profiles of clade Ia and Ib cases.

After estimating susceptibility in children and smallpox-immunised cohorts with historical clade Ia cases in DRC (2011-2015), we found the empirical contact matrix well explained the age distribution of clade Ia cases in DRC in 2024, suggesting community contacts as the main driver of transmission.

Using the same age-dependent susceptibility estimates, we developed an extended model with additional sexual contact routes and fitted it to the age-sex distribution of cases in clade Ib-affected regions to explain the apparent excess among sexually-active age groups.

Our estimates show that sexual contact contributes 41% to the effective reproduction number (Reff) in the Kivus, consistent with clade Ib’s Reff of ~ 1.5 in the Kivus, versus ~0.9 for clade Ia in endemic provinces, underscoring the need for targeted control in high-risk contact settings.

In the 2022 clade IIb outbreak, mpox showed a rapid spread among men who have sex with men (MSM). This time, clade Ib may have found its niche among FSWs, another key population group, to establish steady growth. Our findings reemphasise the importance of prioritising support for those key groups for effective control.

End