PLoS Neglected Tropical Diseases
Volume 11, Issue 5, 2017

The impact of migration and antimicrobial resistance on the transmission dynamics of typhoid fever in Kathmandu, Nepal: A mathematical modelling study (Article) (Open Access)

Saad N.J.* , Bowles C.C. , Grenfell B.T. , Basnyat B. , Arjyal A. , Dongol S. , Karkey A. , Baker S. , Pitzer V.E.
  • a Department of Epidemiology of Microbial Diseases, Yale School of Public Health, Yale University, New Haven, CT, United States
  • b David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, United States
  • c Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, United States, Fogarty International Center, Bethesda, MD, United States
  • d Oxford University Clinical Research Unit, Patan Academy of Health Sciences, Kathmandu, Nepal, Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, United Kingdom
  • e Oxford University Clinical Research Unit, Patan Academy of Health Sciences, Kathmandu, Nepal
  • f Oxford University Clinical Research Unit, Patan Academy of Health Sciences, Kathmandu, Nepal
  • g Oxford University Clinical Research Unit, Patan Academy of Health Sciences, Kathmandu, Nepal
  • h Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, United Kingdom, The Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, United Kingdom
  • i Department of Epidemiology of Microbial Diseases, Yale School of Public Health, Yale University, New Haven, CT, United States, Fogarty International Center, Bethesda, MD, United States

Abstract

Background: A substantial proportion of the global burden of typhoid fever occurs in South Asia. Kathmandu, Nepal experienced a substantial increase in the number of typhoid fever cases (caused by Salmonella Typhi) between 2000 and 2003, which subsequently declined but to a higher endemic level than in 2000. This epidemic of S. Typhi coincided with an increase in organisms with reduced susceptibility against fluoroquinolones, the emergence of S. Typhi H58, and an increase in the migratory population in Kathmandu. Methods: We devised a mathematical model to investigate the potential epidemic drivers of typhoid in Kathmandu and fit this model to weekly data of S. Typhi cases between April 1997 and June 2011 and the age distribution of S. Typhi cases. We used this model to determine if the typhoid epidemic in Kathmandu was driven by heightened migration, the emergence of organisms with reduced susceptibility against fluoroquinolones or a combination of these factors. Results: Models allowing for the migration of susceptible individuals into Kathmandu alone or in combination with the emergence of S. Typhi with reduced susceptibility against fluoroquinolones provided a good fit for the data. The emergence of organisms with reduced susceptibility against fluoroquinolones organisms alone, either through an increase in disease duration or increased transmission, did not fully explain the pattern of S. Typhi infections. Conclusions: Our analysis is consistent with the hypothesis that the increase in typhoid fever in Kathmandu was associated with the migration of susceptible individuals into the city and aided by the emergence of reduced susceptibility against fluoroquinolones. These data support identifying and targeting migrant populations with typhoid immunization programmes to prevent transmission and disease. © 2017 Public Library of Science. All Rights Reserved.

Author Keywords

[No Keywords available]

Index Keywords

Salmonella enterica serovar Typhi transmission Salmonella typhi Human Migration drug effects quinolone derivative human chloramphenicol middle aged typhoid fever Aged sensitivity analysis mathematical model cefixime gatifloxacin disease duration Fluoroquinolones Young Adult ofloxacin Humans Adolescent Treatment Outcome Infant, Newborn male preschool child Aged, 80 and over Infant very elderly Child, Preschool newborn female theoretical model isolation and purification Models, Theoretical Article disease transmission cotrimoxazole gene mutation adult migration amoxicillin antibiotic sensitivity age distribution antibiotic resistance antiinfective agent Nepal Drug Resistance, Bacterial Anti-Bacterial Agents immunization Child
Link
https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020428504&doi=10.1371%2fjournal.pntd.0005547&partnerID=40&md5=e8539d4b701d80875afcd1f18274156b
DOI: 10.1371/journal.pntd.0005547
ISSN: 19352727
Cited by: 4
Original Language: English