Effective collective decision-making in human and animal groups requires robust mechanisms to form consensus, typically via feedback loops in which individuals adapt their behaviour based on their perception of others. Such behaviour has been observed and theorised across scales from nucleosomes to entire societies. Of equal importance, but far less well studied, is the question of how consensus is overturned. In many contexts it is vital that group decisions do not remain fixed in the face of new evidence; echo-chamber effects must be suppressed so that the collective preferences which are expressed are not too strongly entrenched. In this talk I will discuss a new mathematical theory for how consensus can be overturned in symmetric binary choice problems, and compare the theoretical predictions to experiments with human and animal groups.
West Nile virus (WNV) is a vector-borne pathogen causing major outbreaks of West Nile fever worldwide. Although the transmission is maintained via birds and mosquitoes, human infection is possible. Routine surveillance of WNV in the USA is performed by trapping mosquitos and testing for the presence of WNV during the transmission season by RT-qPCR testing. Apart from the general binary positive/negative outcome from these tests, they also generate cycle threshold (Ct) values. Motivated by findings from SARS-CoV-2 viral load dynamics in humans, we hypothesised that Ct values observed through routine pooled testing over time are sufficient to provide information on WNV epidemic dynamics. To investigate this, we introduce an agent-based model of mosquitoes and birds to model WNV epidemiological and viral load dynamics. In this model, we embed a within-host model of the viral load kinetics of mosquitoes. We simulate scenarios where mosquitoes are captured through routine surveillance and tested for WNV through pooled RT-qPCR testing, generating synthetic Ct values over time. We compare our model output to real Ct value data collected through WNV pooled testing in Nebraska in 2022 and 2023.
