Rural-urban gradient in seasonal forcing of measles transmission in Niger

Hdl Handle:
http://hdl.handle.net/10144/117154
Title:
Rural-urban gradient in seasonal forcing of measles transmission in Niger
Authors:
Ferrari, Matthew J; Djibo, Ali; Grais, Rebecca F; Bharti, Nita; Grenfell, Bryan T; Bjornstad, Ottar N
Journal:
Proceedings of The Royal Society Biological Sciences
Abstract:
Seasonally driven cycles of incidence have been consistently observed for a range of directly transmitted pathogens. Though frequently observed, the mechanism of seasonality for directly transmitted human pathogens is rarely well understood. Despite significant annual variation in magnitude, measles outbreaks in Niger consistently begin in the dry season and decline at the onset of the seasonal rains. We estimate the seasonal fluctuation in measles transmission rates for the 38 districts and urban centres of Niger, from 11 years of weekly incidence reports. We show that transmission rates are consistently in anti-phase to the rainfall patterns across the country. The strength of the seasonal forcing of transmission is not correlated with the latitudinal rainfall gradient, as would be expected if transmission rates were determined purely by environmental conditions. Rather, seasonal forcing is correlated with the population size, with larger seasonal fluctuation in more populous, urban areas. This pattern is consistent with seasonal variation in human density and contact rates due to agricultural cycles. The stronger seasonality in large cities drives deep inter-epidemic troughs and results in frequent local extinction of measles, which contrasts starkly to the conventional observation that large cities, by virtue of their size, act as reservoirs of measles.
Affiliation:
The Center for Infectious Disease Dynamics, Department of Biology, The Pennsylvania State University, University Park, PA, USA; The Center for Infectious Disease Dynamics, Department of Entomology, The Pennsylvania State University, University Park, PA, USA; Ministry of Health, Niamey, Niger; Epicentre, Paris, France; Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA; Fogerty Center for International Health, National Institutes of Health, Bethesda, MD, USA
Issue Date:
28-Apr-2010
URI:
http://hdl.handle.net/10144/117154
DOI:
10.1098/rspb.2010.0536
PubMed ID:
20427338
Additional Links:
http://rspb.royalsocietypublishing.org/cgi/pmidlookup?view=long&pmid=20427338
Type:
Article
Language:
en
ISSN:
1471-2954
Appears in Collections:
Other Diseases

Full metadata record

DC FieldValue Language
dc.contributor.authorFerrari, Matthew Jen
dc.contributor.authorDjibo, Alien
dc.contributor.authorGrais, Rebecca Fen
dc.contributor.authorBharti, Nitaen
dc.contributor.authorGrenfell, Bryan Ten
dc.contributor.authorBjornstad, Ottar Nen
dc.date.accessioned2010-12-03T16:21:29Z-
dc.date.available2010-12-03T16:21:29Z-
dc.date.issued2010-04-28-
dc.identifier.citationProc. Biol. Sci. 2010;277(1695):2775-82en
dc.identifier.issn1471-2954-
dc.identifier.pmid20427338-
dc.identifier.doi10.1098/rspb.2010.0536-
dc.identifier.urihttp://hdl.handle.net/10144/117154-
dc.description.abstractSeasonally driven cycles of incidence have been consistently observed for a range of directly transmitted pathogens. Though frequently observed, the mechanism of seasonality for directly transmitted human pathogens is rarely well understood. Despite significant annual variation in magnitude, measles outbreaks in Niger consistently begin in the dry season and decline at the onset of the seasonal rains. We estimate the seasonal fluctuation in measles transmission rates for the 38 districts and urban centres of Niger, from 11 years of weekly incidence reports. We show that transmission rates are consistently in anti-phase to the rainfall patterns across the country. The strength of the seasonal forcing of transmission is not correlated with the latitudinal rainfall gradient, as would be expected if transmission rates were determined purely by environmental conditions. Rather, seasonal forcing is correlated with the population size, with larger seasonal fluctuation in more populous, urban areas. This pattern is consistent with seasonal variation in human density and contact rates due to agricultural cycles. The stronger seasonality in large cities drives deep inter-epidemic troughs and results in frequent local extinction of measles, which contrasts starkly to the conventional observation that large cities, by virtue of their size, act as reservoirs of measles.en
dc.language.isoenen
dc.relation.urlhttp://rspb.royalsocietypublishing.org/cgi/pmidlookup?view=long&pmid=20427338en
dc.rightsArchived with thanks to Proceedings of the Royal Society Biological sciencesen
dc.titleRural-urban gradient in seasonal forcing of measles transmission in Nigeren
dc.typeArticleen
dc.contributor.departmentThe Center for Infectious Disease Dynamics, Department of Biology, The Pennsylvania State University, University Park, PA, USA; The Center for Infectious Disease Dynamics, Department of Entomology, The Pennsylvania State University, University Park, PA, USA; Ministry of Health, Niamey, Niger; Epicentre, Paris, France; Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA; Fogerty Center for International Health, National Institutes of Health, Bethesda, MD, USAen
dc.identifier.journalProceedings of The Royal Society Biological Sciencesen

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