Lassa fever outbreaks, mathematical models, and disease parameters: a systematic review and meta-analysis

Patrick Doohan, David Jorgensen, Tristan M. Naidoo, Kelly McCain, Joseph T. Hicks, Ruth McCabe, Sangeeta Bhatia, Kelly Charniga, Gina Cuomo-Dannenburg, Arran Hamlet, Rebecca K. Nash, Dariya Nikitin, Thomas Rawson, Richard J. Sheppard, H. Juliette T. Unwin, Sabine van Elsland, Anne Cori, Christian Morgenstern*, Natsuko Imai-Eaton*, Aaron MorrisAlpha Forna, Amy Dighe, Anna Vicco, Anna Maria Hartner, Ben Lambert, Bethan Cracknell Daniels, Charlie Whittaker, Cosmo Santoni, Cyril Geismar, Dominic Dee, Ed Knock, Ettie Unwin, Hayley Thompson, Ilaria Dorigatti, Isobel Routledge, Jack Wardle, Janetta Skarp, Joseph Hicks, Kanchan Parchani, Keith Fraser, Kieran Drake, Lily Geidelberg, Lorenzo Cattarino, Mantra Kusumgar, Mara Kont, Marc Baguelin, Pablo Perez Guzman, Paul Lietar, Paula Christen, Rebecca Nash, Rich Fitzjohn, Richard Sheppard, Rob Johnson, Sequoia Leuba, Shazia Ruybal-Pesantez, Sreejith Radhakrishnan, Tristan Naidoo, Zulma Cucunuba Perez

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Background: Understanding the epidemiological parameters and transmission dynamics of Lassa fever, a significant public health threat in west Africa caused by the rodent-borne Lassa virus, is crucial for informing evidence-based interventions and outbreak response strategies. Therefore, our study aimed to collate and enhance understanding of the key epidemiological parameters of Lassa fever. Methods: We conducted a systematic review, searching PubMed and Web of Science for peer-reviewed studies published from database inception up to June 13, 2024, to compile and analyse key epidemiological parameters, mathematical models, and outbreaks of Lassa fever. English-language, peer-reviewed, original research articles were included if they reported on Lassa fever outbreak sizes, transmission models, viral evolution, transmission, natural history, severity, seroprevalence, or risk factors. Non-peer-reviewed literature was excluded. Data were extracted by two independent individuals from published literature, focusing on seroprevalence, transmissibility, epidemiological delays, and disease severity. We performed a meta-analysis to calculate pooled estimates of case-fatality ratios (CFRs) and the delay from symptom onset to hospital admission. This study is registered with PROSPERO (identifier number CRD42023393345). Findings: The database search returned 5614 potentially relevant studies, and a further 16 studies were identified from backward citation chaining. After de-duplication and exclusion, 193 publications met our inclusion criteria and provided 440 relevant parameter estimates in total. Although Lassa virus is endemic in west Africa, the spatiotemporal coverage of general-population seroprevalence estimates (ranging from 2·6% [6/232] to 58·2% [103/177]) was poor, highlighting the spatial uncertainty in Lassa fever risk. Similarly, only four basic reproduction number estimates (ranging from 1·13 to 1·40) were available. We estimated a pooled total random effect CFR of 33·5% (95% CI 25·8–42·2, I2=95%) and found potential variation in severity by geographical regions typically associated with specific Lassa virus lineages. We estimated a pooled total random effect mean symptom-onset-to-hospital-admission delay of 8·19 days (95% CI 7·31–9·06, I2=93%), but other epidemiological delays were poorly characterised in the existing literature. Interpretation: Our findings highlight the absence of empirical Lassa fever parameter estimates despite its high burden in west Africa. Improved surveillance approaches to capture mild cases in humans and to further cover rodent populations are needed to better understand Lassa fever transmission dynamics. Addressing these gaps is essential for developing accurate mathematical models and informing evidence-based interventions to mitigate the effect of Lassa fever on public health in endemic regions. Funding: UK Medical Research Council, National Institute for Health and Care Research, Academy of Medical Sciences, Wellcome, UK Department for Business, Energy, and Industrial Strategy, British Heart Foundation, Diabetes UK, Schmidt Foundation, Community Jameel, Royal Society, and Imperial College London. Translation: For the French translation of the abstract see Supplementary Materials section.

Original languageEnglish
Pages (from-to)e1962-e1972
JournalThe Lancet Global Health
Volume12
Issue number12
DOIs
Publication statusPublished - Dec 2024
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2024 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license

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