title: Detecting differential transmissibilities that affect the size of self-limited outbreaks.
abstract: Our ability to respond appropriately to infectious diseases is enhanced by identifying differences in the potential for transmitting infection between individuals. Here, we identify epidemiological traits of self-limited infections (i.e. infections with an effective reproduction number satisfying [0 < R eff < 1) that correlate with transmissibility. Our analysis is based on a branching process model that permits statistical comparison of both the strength and heterogeneity of transmission for two distinct types of cases. Our approach provides insight into a variety of scenarios, including the transmission of Middle East Respiratory Syndrome Coronavirus (MERS-CoV) in the Arabian peninsula, measles in North America, pre-eradication smallpox in Europe, and human monkeypox in the Democratic Republic of the Congo. When applied to chain size data for MERS-CoV transmission before 2014, our method indicates that despite an apparent trend towards improved control, there is not enough statistical evidence to indicate that R eff has declined with time. Meanwhile, chain size data for measles in the United States and Canada reveal statistically significant geographic variation in R eff, suggesting that the timing and coverage of national vaccination programs, as well as contact tracing procedures, may shape the size distribution of observed infection clusters. Infection source data for smallpox suggests that primary cases transmitted more than secondary cases, and provides a quantitative assessment of the effectiveness of control interventions. Human monkeypox, on the other hand, does not show evidence of differential transmission between animals in contact with humans, primary cases, or secondary cases, which assuages the concern that social mixing can amplify transmission by secondary cases. Lastly, we evaluate surveillance requirements for detecting a change in the human-to-human transmission of monkeypox since the cessation of cross-protective smallpox vaccination. Our studies lay the foundation for future investigations regarding how infection source, vaccination status or other putative transmissibility traits may affect self-limited transmission.
authors.affiliation: Francis I. Proctor Foundation, University of California San Francisco, San Francisco, California, United States of America; Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America.
authors.forename: Seth
authors.initials: S
authors.lastname: Blumberg
authors.affiliation: Centre for the Mathematical Modelling of Infectious Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom; Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, United States of America.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Funk
authors.affiliation: Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America; Department of Biology, University of Florida, Gainesville, Florida, United States of America; Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Juliet R C
authors.initials: JR
authors.lastname: Pulliam
mesh_terms: D018352:Coronavirus Infections / Q000453:epidemiology* / Q000517:prevention & control / Q000635:transmission; D015023:Democratic Republic of the Congo / Q000453:epidemiology; D004196:Disease Outbreaks; D005060:Europe / Q000453:epidemiology; D006801:Humans; D008457:Measles / Q000453:epidemiology* / Q000517:prevention & control / Q000635:transmission; D008877:Middle East / Q000453:epidemiology; D065207:Middle East Respiratory Syndrome Coronavirus; D008954:Models, Biological; D045908:Mpox, Monkeypox / Q000453:epidemiology* / Q000517:prevention & control / Q000635:transmission; D009656:North America / Q000453:epidemiology; D012899:Smallpox / Q000453:epidemiology* / Q000517:prevention & control / Q000635:transmission; D013269:Stochastic Processes; D014611:Vaccination