Intra-Household Transmission of Shigella in an Urban Slum in Nairobi, Kenya Público

Abstract

Background: Worldwide, secondary attack rates of shigellosis in households have been found to be as high as 40%. While shigellosis incidence has been studied in urban informal settlements in Kenya, data on the transmission of Shigella within families and households are limited. Using population-based surveillance in an urban slum in Kenya, we performed a descriptive analysis of the frequency and possible transmission of shigellosis within households and calculated the incidence of diarrhea among shigellosis cases and their household contacts.

Methods: Population-based data were collected from periodic household interviews and stool specimens were collected for laboratory testing. We calculated the number of laboratory diagnosed shigellosis cases that belonged to common households (households with multiple cases) and the incidence of diarrhea in those households during the month before and after diagnosis. Households that saw one or more cases were stratified by time between cases and by number of household inhabitants.

Results: Shigella species were isolated from 508 (18%) of 2855 specimens tested. Approximately 18.5% of cases were from common households. Overall, 9% of households with one case of shigellosis had a second case. Households with ≥5 inhabitants were twice as likely to have a subsequent case diagnosed at any time during the study period. Among all household inhabitants, diarrhea incidence was higher in the month before the diagnosis of a shigellosis case in that household, than in the month after the diagnosis.

Conclusion: Confirmed shigellosis cases were frequently identified from common households. Larger households were at greatest risk for subsequent cases. Promotion of improved water, sanitation, and hygiene practices among household members is essential to prevent household transmission of Shigella in crowded settings. Interventions in informal settlements must consider targeting larger households and households with inhabitants in the age groups most at risk.

Table of Contents

CHAPTER 1: Introduction ...........................................................................1

CHAPTER 2: Literature Review ...................................................................4
Shigella Characteristics and Clinical Features ...................................................4
Transmission of Shigella and Risk Factors for Severe Disease and Death ..............5
Diagnosis, Treatment, and Prevention ............................................................7
Household Transmission and Secondary Cases .................................................8
Global Burden of Shigellosis ........................................................................10
Shigellosis in Kenya ...................................................................................11

CHAPTER 3: Manuscript ............................................................................13
Abstract ...................................................................................................13
Methodology .............................................................................................15
Study site ................................................................................................15
Surveillance and laboratory procedures ........................................................16
Period of study .........................................................................................18
Case definitions ........................................................................................18
Analysis ..................................................................................................19
Ethical considerations ................................................................................22
Results ....................................................................................................23
Demographics ..........................................................................................23
Shigellosis within households ......................................................................24
Clinical characteristics ...............................................................................26
Discussion ...............................................................................................27
References ..............................................................................................32
Tables and Figures ....................................................................................36

CHAPTER 4: Conclusions and Recommendations ........................................45
References ...............................................................................................47

About this Master's Thesis

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School	Rollins School of Public Health
Department	Hubert Department of Global Health
Degree	MPH
Submission	Master's Thesis
Language	English
Research Field	Health Sciences, Public Health Health Sciences, Epidemiology
Palabra Clave	intra-household family shigellosis intra-familial slum Kenya Shigella household informal settlement transmission
Committee Chair / Thesis Advisor	Brachman, Philip S, Emory University
Committee Members	Mintz, Eric Daniel, Emory University O'Reilly, Ciara, CDC Von, Nguyen, CDC
Partnering Agencies	Non-US governmental agency (e.g., Minister of Health in Haiti) CDC

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