title: A Unified Framework for the Infection Dynamics of Zoonotic Spillover and Spread.
abstract: A considerable amount of disease is transmitted from animals to humans and many of these zoonoses are neglected tropical diseases. As outbreaks of SARS, avian influenza and Ebola have demonstrated, however, zoonotic diseases are serious threats to global public health and are not just problems confined to remote regions. There are two fundamental, and poorly studied, stages of zoonotic disease emergence: 'spillover', i.e. transmission of pathogens from animals to humans, and 'stuttering transmission', i.e. when limited human-to-human infections occur, leading to self-limiting chains of transmission. We developed a transparent, theoretical framework, based on a generalization of Poisson processes with memory of past human infections, that unifies these stages. Once we have quantified pathogen dynamics in the reservoir, with some knowledge of the mechanism of contact, the approach provides a tool to estimate the likelihood of spillover events. Comparisons with independent agent-based models demonstrates the ability of the framework to correctly estimate the relative contributions of human-to-human vs animal transmission. As an illustrative example, we applied our model to Lassa fever, a rodent-borne, viral haemorrhagic disease common in West Africa, for which data on human outbreaks were available. The approach developed here is general and applicable to a range of zoonoses. This kind of methodology is of crucial importance for the scientific, medical and public health communities working at the interface between animal and human diseases to assess the risk associated with the disease and to plan intervention and appropriate control measures. The Lassa case study revealed important knowledge gaps, and opportunities, arising from limited knowledge of the temporal patterns in reporting, abundance of and infection prevalence in, the host reservoir.
authors: Department of Veterinary Medicine, Disease Dynamics Unit, University of Cambridge, Cambridge, United Kingdom.|Environmental Change Department, Centre for Radiation, Chemical and Environmental Hazards, Public Health England, London, United Kingdom.
authors: Giovanni
authors: 0000-0002-6150-2843
authors: G
authors: Lo Iacono
authors: Institute of Zoology, Zoological Society of London, United Kingdom.
authors: Andrew A
authors: AA
authors: Cunningham
authors: Bernhard-Nocht Institute of Tropical Medicine, Hamburg, Germany.
authors: Elisabeth
authors: E
authors: Fichet-Calvet
authors: Department of Microbiology and Immunology, Tulane University, New Orleans, Louisiana, United States of America.
authors: Robert F
authors: RF
authors: Garry
authors: Lassa Fever Program, Kenema Government Hospital, Kenema, Sierra Leone.
authors: Donald S
authors: DS
authors: Grant
authors: Institute of Development Studies, University of Sussex, Brighton, United Kingdom.
authors: Melissa
authors: M
authors: Leach
authors: Department of Microbiology and Immunology, Tulane University, New Orleans, Louisiana, United States of America.
authors: Lina M
authors: LM
authors: Moses
authors: Gastrointestinal, Emerging and Zoonotic Infections, Public Health England, London, United Kingdom.
authors: Gordon
authors: G
authors: Nichols
authors: Sections of Infectious Disease, Departments of Pediatrics and Internal Medicine, School of Medicine, Tulane University, New Orleans, Louisiana, United States of America.
authors: John S
authors: JS
authors: Schieffelin
authors: Department of Biostatistics and Bioinformatics, Tulane School of Public Health and Tropical Medicine, New Orleans, Louisiana, United States of America.
authors: Jeffrey G
authors: JG
authors: Shaffer
authors: Department of Biology, Colorado State University, Fort Collins, Colorado, United States of America.
authors: Colleen T
authors: CT
authors: Webb
authors: Department of Veterinary Medicine, Disease Dynamics Unit, University of Cambridge, Cambridge, United Kingdom.
authors: James L N
authors: JL
authors: Wood
mesh_terms: D000818:Animals; D004196:Disease Outbreaks / Q000517:prevention & control*; D004198:Disease Susceptibility; D006801:Humans; D007835:Lassa Fever / Q000635:transmission*; D008962:Models, Theoretical; D012377:Rodentia / Q000821:virology; D015047:Zoonoses / Q000635:transmission*