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# West Nile virus activity in Arizona linked to drought-monsoon cycles in modelling study
- URL: https://www.coios.me/west-nile-virus-activity-in-arizona-linked-to-drought/
- Published: 2026-11-08T13:05:18.000Z
- Updated: 2026-11-08T14:10:18.000Z
- Description: Models built on Arizona mosquito surveillance explained 65.3% of weekly variation in county-level human West Nile cases, one week ahead.
- Author: Daniel Ryan
- Tags: Tomorrow's world, A changing climate, Infection and pandemics, United States, #preprint, #new, #item, #source-2026-11, #score-65

This preprint applied random forest models to 652,897 Arizona mosquito trap records from 2013 to 2023\. Predictors included weather averaged over preceding weeks. Averaged across 44 models, it predicted whether trapped Culex pools tested positive for West Nile virus with 98.9% accuracy. Modelled virus activity explained 65.3% of weekly variation in county-level human cases, which followed one week later. Projections to 2100 showed significant rises in weeks of virus activity over 0.6% to 39.4% of Arizona, by scenario. The projections include only direct climatic effects, leaving out urbanisation, water management and mosquito adaptation.

*Why it is interesting: Mosquito abundance and virus occurrence did not fall at Arizona's extreme summer heat, suggesting thermal refugia. Drought followed by monsoon rain, rather than temperature alone, was the main driver of activity.*

Source

[bioRxiv : the preprint server for biology, 6 November 2026](https://doi.org/10.64898/2026.10.28.762036?ref=coios.me)

DOI

10.64898/2026.10.28.762036

Full text

[Open copy](https://www.biorxiv.org/content/biorxiv/early/2026/10/30/2026.10.28.762036.full.pdf?ref=coios.me) (authors' accepted manuscript, repository)

Type

Preprint

Design

Random forest spatial-temporal model of Culex abundance and West Nile virus occurrence, \~10 years of Arizona mosquito surveillance with time-lagged weather, weekly county resolution, plus climate-scenario projections to 2100

Verdict

New finding

Driver

[A changing climate](https://www.coios.me/d-climate/)

Driver

[Infection and pandemics](https://www.coios.me/d-infectious-disease/)