When a mosquito takes blood from an infected host, the virus must cross several biological barriers inside the insect before it can be transmitted to a new host. This process, known as the extrinsic incubation period (EIP), is a key driver of vector-borne disease dynamics. Most epidemiological models simplify it by assuming the EIP follows an exponential distribution, meaning all exposed mosquitoes are treated as equally likely to become infectious at any given point after exposure.
In a study published in PLOS Computational Biology, our partners at INRAE challenge this assumption. Loisel et al. built a stochastic model that tracks how the virus progresses through three successive barriers inside the mosquito (infection, dissemination, and transmission), and fitted it to experimental data from Aedes mosquitoes infected with dengue, Zika, and chikungunya using an ABC-SMC statistical approach. Their results show that the exponential assumption does not hold in most cases, particularly for dengue and Zika. The framework is generic, adaptable to other arboviruses, and can be linked to larger population-scale models to improve epidemic predictions and inform control strategies.
Loisel, L., Raquin, V., Ratinier, M., Ezanno, P. & Beaunée, G. Intra-vector infection dynamics challenge how to model the extrinsic incubation period for major arboviruses: dengue, Zika, and chikungunya. PLOS Computational Biology (2025). https://doi.org/10.1371/journal.pcbi.1013393
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