Demographics of Natural Oral Infection of Mosquitos by Venezuelan Equine Encephalitis Virus

The within-host diversity of virus populations can be drastically limited during between-host transmission, with primary infec-tion of hosts representing a major constraint to diversity maintenance. However, there is an extreme paucity of quantitative data on the demographic changes experienced by virus populations during primary infection. Here, the multiplicity of cellular infec-tion (MOI) and population bottlenecks were quantified during primary mosquito infection by Venezuelan equine encephalitis virus, an arbovirus causing neurological disease in humans and equids. RNA viral infections generally generate large and diverse pop-ulations within the infected host. This diversity plays a key role in important epidemiological and evolutionary processes (1–3). However, several steps during transmission can constrain the de-mographics and genetics of the virus population, with host pri-mary infection being one of the main barriers. During primary infection, the number of initially infected cells is not infinite, potentially lowering the size and genetic diversity of the colonizing population compared to that present in the donor host. The multiplicity of cellular infection (MOI) in those cells is thus a fundamental parameter determining the demographics an