Academic journal article Bulletin of the World Health Organization

The Population-Based Burden of Influenza-Associated Hospitalization in Rural Western Kenya, 2007-2009/ la Charge Basee Sur la Population De L'hospitalisation Liee a la Qrippe Dans Les Regions Rurales De L'ouest Du Kenya, 2007-2009/ la Carga Demografica De Las Hospitalizaciones Asociadas a la Gripe En El Oeste Rural De Kenya, 2007-2009

Academic journal article Bulletin of the World Health Organization

The Population-Based Burden of Influenza-Associated Hospitalization in Rural Western Kenya, 2007-2009/ la Charge Basee Sur la Population De L'hospitalisation Liee a la Qrippe Dans Les Regions Rurales De L'ouest Du Kenya, 2007-2009/ la Carga Demografica De Las Hospitalizaciones Asociadas a la Gripe En El Oeste Rural De Kenya, 2007-2009

Article excerpt

Introduction

Although influenza has been widely studied in developed countries, little is known about its epidemiology, seasonality and burden in developing countries. (1-6) The epidemiology of influenza and the hospitalization rates associated with the illness may be different in sub-Saharan Africa and more developed areas for several reasons. In temperate regions influenza is highly seasonal, with transmission peaking during winter, whereas in the tropics influenza viruses are thought to circulate year round. (7) In Africa, the risk factors for severe outcomes from influenza, such as chronic heart disease, chronic lung disease, infection with human immunodeficiency virus (HIV) and smoking, differ from those found in Europe and North America. (4,8-10) Regional differences in the age distribution of human populations and their use of health services may also affect the rate of hospitalization for influenza.

In Kenya, people hospitalized with respiratory illnesses are rarely tested for viral pathogens. Influenza vaccine and drugs active against influenza viruses are not readily available, and little is known about the relative contribution of influenza to severe respiratory disease. In any country, data on influenza can help guide clinical management and allow the health ministry to estimate the influenza burden so that the potential impact of targeted interventions, such as immunization, can be assessed.

Following the 2006 outbreak of avian influenza in Nigerian poultry, Kenya established prospective surveillance for human influenza in several hospitals, with particular emphasis on the detection of the H5N1 subtype of the influenza A virus. (11) We describe here the results of population-based, district-wide surveillance in western Kenya for hospitalization with influenza virus in the two years before A(H1N1)pdm09 reached Kenya. (12)

Methods

Study site

The study was based in the Bondo district of western Kenya, which had a population of 238 780 at the time of the 1999 national census. The district's population is culturally homogenous and almost entirely rural and poor, as it consists mainly of individuals of Luo ethnicity who live by subsistence farming and fishing. (13) Most roads in the district are unpaved. The area is holoendemic for malaria and has a high child mortality rate (212 deaths per 1000 live births in 2008). (13) It also has a high prevalence of HIV infection in young adults. In 2003-2004, for example, HIV prevalence was 15.4%, or twice the corresponding national value, among those aged 13-34 years who lived in Bondo district. (8)

Bondo district has seven inpatient facilities, including one district hospital, as well as 45 outpatient health facilities. The residents of Bondo district seek care in these facilities and also from private local providers, traditional healers, drug sellers and community health workers. (14) The hospital in the neighbouring district of Siaya and the provincial hospital in Kisumu are 27 and 57 km from Bondo town, respectively, and rarely admit patients from Bondo district. (15) In one part of Bondo district, 25 000 people are offered free, high-quality care at Lwak Mission Hospital, including admission, as part of population-based infectious disease surveillance. (16, 7) Influenza vaccination is not available in the district in either the public or the private sector.

Data collection

In May 2007, the United States Centers for Disease Control and Prevention (CDC) and the Kenya Medical Research Institute (KEMRI) established prospective population-based surveillance for influenza in all seven inpatient facilities in Bondo district. Trained surveillance officers, mostly nurses, enrolled all consenting patients who were hospitalized for respiratory illness, defined as cough, difficulty breathing or (for patients aged [greater than or equal to] 5 years) pleuritic chest pain. Patients who had had a cough for more than 2 weeks when they presented were excluded because the study's focus was on acute respiratory illness. …

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