Unravelling the Impact of Environmental Drivers on Infectious Diseases: The Case of Campylobacter

Background: Disentangling the impact of the environment on infectious diseases is crucial for health protection, preparedness and prevention. This is particularly relevant to campylobacteriosis, one of the most common bacterial food borne diseases worldwide. The incidence displays consistent but, despite many hypotheses, unexplained seasonality.Attributing and quantifying the contribution of environmental factors (e.g. temperature, humidity, wind, day length) to the burden of the disease is challenging. For example, discerning the time of onset and the duration of the impact of environmental factors on the likelihood of infection (time-lag) is difficult.  Methods: We developed a novel modeling approach exploiting the linkage of approximately one- million campylobacteriosis cases over 25 years in England and Wales with meteorological datasets from diagnostic laboratory locations.  Findings: We were able to identify the non-linear relationships for the incidence of campylobacteriosis cases conditional upon environmental variables.We found that the incidence depends non-monotonically with maximum air temperature and tends to reach a peak for relative humidity at around $80\%$.The analysis demonstrated that different environmental factors resulted in different time-lags and that these lags varied with season rather than being fixed values.Finally, maximum air temperature and relative humidity are estimated to contribute equally as drivers of the burden of campylobacteriosis and their contribution is twice that of day length. Interpretation: This study enhances our understanding of the dynamics at the environment-disease interface, and allows us to predict infectious disease incidence by exploiting the databases and knowledge of the history of relevant environmental variables. Funding Statement: This research was funded in part by the UK Medical Research Council (MRC) and the UK Natural Environment Council (NERC) for the MEDMI Project (MR/K019341/1); the European Union’s Horizon 2020 Research and Innovation programme under grant agreement No 773830: One Health European Joint Programme; the National Institute for Health Research Health Protection Research Unit (NIHR HPRU) in Environmental Change and Health at the London School of Hygiene and Tropical Medicine in partnership with Public Health England (PHE), and in collaboration with the University of Exeter, University College London, and the Met Office. Declaration of Interests: None to declare.