Factors associated with increased risk of progression to respiratory syncytial virus-associated pneumonia in young Kenyan children

Abstract

Objectives: To identify factors associated with developing severe respiratory syncytial virus (RSV) pneumonia and their commonality with all-cause lower respiratory tract infection (LRTI), in order to isolate those risk factors specifically associated with RSV-LRTI and identify targets for control.

Methods: A birth cohort of rural Kenyan children was intensively monitored for acute respiratory infection (ARI) over three RSV epidemics. RSV was diagnosed by immunofluorescence of nasal washings collected at each ARI episode. Cox regression was used to determine the relative risk of disease for a range of co-factors.

Results: A total of 469 children provided 937 years of follow-up, and experienced 857 all-cause LRTI, 362 RSV-ARI and 92 RSV-LRTI episodes. Factors associated with RSV-LRTI, but not RSV-ARI, were severe stunting (z-score < or =-2, RR 1.7 95%CI 1.1-2.8), crowding (increased number of children, RR 2.6, 1.0-6.5) and number of siblings under 6 years (RR 2.0, 1.2-3.4). Moderate and severe stunting (z-score < or =-1), crowding and a sibling aged over 5 years sleeping in the same room as the index child were associated with increased risk of all-cause LRTI, whereas higher educational level of the primary caretaker was associated with protection.

Conclusion: We identify factors related to host nutritional status (stunting) and contact intensity (crowding, siblings) which are distinguishable in their association with RSV severe disease in infant and young child. These factors are broadly in common with those associated with all-cause LRTI. The results support targeted strategies for prevention.

Figure 1

Descriptive characteristics of cases identified during the study. The bars represent the absolute numbers of cases of RSV-ARI (white bars), RSV-LRTI (grey bars) and all-cause LRTI (black bars) by specific age category.

Figure 2

Weight for age, height for age, weight for height z–scores of children in the study by sex and age. The box plot depicts the interquartile range as a box and the median as a line in the box. Bars, upper and lower adjacent values and dots represent outliers.