Heterogeneity in social and epidemiological factors determines the risk of measles outbreaks

Paolo Bosetti; Piero Poletti; Massimo Stella; Bruno Lepri; Stefano Merler; Manlio De Domenico

doi:10.1073/pnas.1920986117

New Research In

Edited by Roy M. Anderson, Imperial College London, London, UK, and accepted by Editorial Board Member Simon A. Levin October 1, 2020 (received for review November 29, 2019)

Significance

The recent increase in large-scale migration trends generates several concerns about public health in destination countries, especially in the presence of massive incoming human flows from countries with a disrupted healthcare system. Here, we analyze the flow of 3.5 M Syrian refugees toward Turkey to quantify the risk of measles outbreaks. Our results suggest that heterogeneity in immunity, population distribution, and human-mobility flows is mostly responsible for such a risk: In fact, adequate policies of social integration and vaccine campaigns provide the most effective strategies to reduce measles disease risks for both migrant and hosting populations.

Abstract

Political and environmental factors—e.g., regional conflicts and global warming—increase large-scale migrations, posing extraordinary societal challenges to policymakers of destination countries. A common concern is that such a massive arrival of people—often from a country with a disrupted healthcare system—can increase the risk of vaccine-preventable disease outbreaks like measles. We analyze human flows of 3.5 million (M) Syrian refugees in Turkey inferred from massive mobile-phone data to verify this concern. We use multilayer modeling of interdependent social and epidemic dynamics to demonstrate that the risk of disease reemergence in Turkey, the main host country, can be dramatically reduced by 75 to 90% when the mixing of Turkish and Syrian populations is high. Our results suggest that maximizing the dispersal of refugees in the recipient population contributes to impede the spread of sustained measles epidemics, rather than favoring it. Targeted vaccination campaigns and policies enhancing social integration of refugees are the most effective strategies to reduce epidemic risks for all citizens.

Footnotes

↵¹P.B. and P.P. contributed equally to this work.
↵²To whom correspondence may be addressed. Email: poletti{at}fbk.eu.
↵³S.M. and M.D.D. contributed equally to this work.

Author contributions: P.B., P.P., B.L., S.M., and M.D.D. designed research; P.B., P.P., M.S., B.L., S.M., and M.D.D. performed research; P.B., P.P., and M.S. analyzed data; and P.B., P.P., M.S., B.L., S.M., and M.D.D. wrote the paper.
The authors declare no competing interest.
This article is a PNAS Direct Submission. R.M.A. is a Guest Editor invited by the Editorial Board.
This article contains supporting information online at https://www.pnas.org/lookup/suppl/doi:10.1073/pnas.1920986117/-/DCSupplemental.

Data Availability.

The mobile-phone data were received for the Data for Refugees Turkey Challenge (D4R) and were open for analysis only to the registered and accepted teams, including ours. Other datasets we used are publicly available. To protect the privacy of the users (Turkish citizens and Syrian refugees), mobile-phone data cannot be shared by the authors. The findings presented in our work can be replicated by using publicly available datasets and by asking for data access for relevant mobile-phone datasets from TT. Interested researchers should apply for data access by contacting TT at d4r@turktelekom.com.tr. Code and data required to reproduce the main findings of the paper are publicly available on Zenodo at https://zenodo.org/record/4227667 (62) and upon request to TT.

Published under the PNAS license.

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