Abstract
BackgroundFew comprehensive data exist on disease incidence for specific etiologies of acute respiratory illness (ARI) in older children and adults in Africa.Methodology/Principal FindingsFrom March 1, 2007, to February 28, 2010, among a surveillance population of 21,420 persons >5 years old in rural western Kenya, we collected blood for culture and malaria smears, nasopharyngeal and oropharyngeal swabs for quantitative real-time PCR for ten viruses and three atypical bacteria, and urine for pneumococcal antigen testing on outpatients and inpatients meeting a ARI case definition (cough or difficulty breathing or chest pain and temperature >38.0°C or oxygen saturation <90% or hospitalization). We also collected swabs from asymptomatic controls, from which we calculated pathogen-attributable fractions, adjusting for age, season, and HIV-status, in logistic regression. We calculated incidence by pathogen, adjusting for health-seeking for ARI and pathogen-attributable fractions. Among 3,406 ARI patients >5 years old (adjusted annual incidence 12.0 per 100 person-years), influenza A virus was the most common virus (22% overall; 11% inpatients, 27% outpatients) and Streptococcus pneumoniae was the most common bacteria (16% overall; 23% inpatients, 14% outpatients), yielding annual incidences of 2.6 and 1.7 episodes per 100 person-years, respectively. Influenza A virus, influenza B virus, respiratory syncytial virus (RSV) and human metapneumovirus were more prevalent in swabs among cases (22%, 6%, 8% and 5%, respectively) than controls. Adenovirus, parainfluenza viruses, rhinovirus/enterovirus, parechovirus, and Mycoplasma pneumoniae were not more prevalent among cases than controls. Pneumococcus and non-typhi Salmonella were more prevalent among HIV-infected adults, but prevalence of viruses was similar among HIV-infected and HIV-negative individuals. ARI incidence was highest during peak malaria season.Conclusions/SignficanceVaccination against influenza and pneumococcus (by potential herd immunity from childhood vaccination or of HIV-infected adults) might prevent much of the substantial ARI incidence among persons >5 years old in similar rural African settings.
Highlights
Compared with other regions, the mortality rate among older children and adults remains several-fold higher in sub-Saharan Africa, where acute respiratory infections (ARI) are a leading cause of this high mortality, as well as associated morbidity [1]
The percentage of patients with S. pneumoniae identified increased to 16% when adding urine antigen results to blood cultures (23% inpatients versus 14% outpatients, p = 0.003)
We demonstrated different etiologic predominance for the same broadly defined acute respiratory illness (ARI) syndrome based on hospitalization status, with pneumococcus more common among inpatients and influenza viruses and human metapneumovirus (hMPV) among outpatients
Summary
The mortality rate among older children and adults remains several-fold higher in sub-Saharan Africa, where acute respiratory infections (ARI) are a leading cause of this high mortality, as well as associated morbidity [1]. Data on etiologies and rates of ARI among persons $5 years old in Africa have been principally focused on few geographic areas and pathogens (e.g., pneumococcus, tuberculosis). Few studies have comprehensively examined the etiologies of ARI among Africans $5 years of age. There is even less available data on disease incidence for specific etiologies, which can inform public health policies regarding treatment and prevention. Few comprehensive data exist on disease incidence for specific etiologies of acute respiratory illness (ARI) in older children and adults in Africa
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