The age distribution of dengue, Zika, and chikungunya cases is remarkably consistent across different outbreak sizes, geographic regions, time periods, and population scales. Despite enormous variation in total case counts -- from small local outbreaks to national epidemics -- the proportion of cases in each age group holds steady. In contrast, infections transmitted by other vectors (malaria by Anopheles, leishmaniasis by sandflies) show distinctly different and less stable age patterns.
The authors conclude that for Aedes-transmitted diseases, the age distribution is determined primarily by the ecological interaction between the mosquito and its human hosts, not by the epidemiology of the pathogen itself. Three different viruses, with different immunological profiles and different clinical presentations, produce the same age curve because they share the same vector. The mosquito's biting preferences, activity patterns, and habitat overlap with different age groups imprint a signature on the case distribution that the pathogen cannot override.
This is a case where the delivery mechanism dominates the content. The virus determines what disease you get; the vector determines who gets it. And because the vector-host interaction is more stable than the virus-host interaction -- mosquito behavior varies less than immune history -- the age distribution becomes a fingerprint of the transmission route rather than the transmitted agent. In any system where the channel of delivery is shared across different payloads, the channel's properties may leave a stronger demographic imprint than the payload's properties.
(arXiv:2603.16773)