Respiratory syncytial virus infection in Navajo and White Mountain Apache children

Objective. The hospitalization rate for bronchiolitis of any cause among US children younger than 1 year is estimated at 31.2 per 1000. No data exist on respiratory syncytial virus (RSV)-specific hospitalization rates among high-risk Native Americans other than Alaska Natives, for whom the incidence of RSV hospitalization was estimated at 150 per 1000 among infants younger than 1 year. We aimed to estimate RSV hospitalization rates among Navajo and White Mountain Apache children younger than 2 years. Methods. We conducted prospective population-level hospital-based surveillance to determine RSV hospitalization rates among Navajo and White Mountain Apache children younger than 2 years. From 1997 to 2000, all children who were admitted for acute lower respiratory tract infection between October 1 and March 31 had a nasopharyngeal aspirate obtained and tested for RSV by commercial enzyme immunoassay kits. We reviewed charts of children who tested positive for RSV antigen to determine disease severity. Results. During 3 RSV seasons (1997-2000), 51.3% of 1837 admissions for acute lower respiratory tract infection among children younger than 2 years were attributed to RSV infection. The overall seasonal RSV hospitalization rate among children younger than 2 years was 63.6 per 1000 and 91.3 per 1000 among children younger than 1 year. In a univariate analysis, predictors of severity included age <6 months (relative risk: 6.8; 95% confidence interval: 3.1-17.0). Conclusions. Navajo and White Mountain Apache children are at high risk for RSV disease requiring hospitalization. A lower threshold for hospitalization or underlying chronic conditions that predispose to severe RSV disease do not seem to explain high RSV hospitalization rates in this population.