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The symptoms of many infectious diseases influence their host to withdraw from social activity limiting their potential to spread. Successful transmission therefore requires the onset of infectiousness to coincide with a time when the host is socially active. Since social activity and infectiousness are both temporal phenomena, Colman, et al. (2018) hypothesize that diseases are most pervasive when these two processes are synchronized.
The researchers considered disease dynamics that incorporate behavioral responses that effectively shorten the infectious period of the pathogen. Using data collected from face-to-face social interactions and synthetic contact networks constructed from empirical demographic data, they measured the reachability of this disease model and perform disease simulations over a range of latent period durations.
They found that maximum transmission risk results when the disease latent period (and thus the generation time) are synchronized with human circadian rhythms of 24 h, and minimum transmission risk when latent periods are out of phase with circadian rhythms by 12 hours. The effect of this synchronization is present for a range of disease models with realistic disease parameters and host behavioral responses.
The researchers conclude that the reproductive potential of pathogens is linked inextricably to the host social behavior required for transmission. They propose that future work should consider contact periodicity in models of disease dynamics, and suggest the possibility that disease control strategies may be designed to optimize against the effects of synchronization.
Source: Colman E, Spies K and Bansal S. The reachability of contagion in temporal contact networks: how disease latency can exploit the rhythm of human behavior. BMC Infectious Diseases. 2018;18:219