The burden of hospitalized lower respiratory tract infection due to respiratory syncytial virus in rural Thailand

Abstract

Background: We describe the epidemiology of hospitalized RSV infections for all age groups from population-based surveillance in two rural provinces in Thailand.

Methods: From September 1, 2003 through December 31, 2007, we enrolled hospitalized patients with acute lower respiratory tract illness, who had a chest radiograph ordered by the physician, from all hospitals in SaKaeo and Nakhom Phanom Provinces. We tested nasopharyngeal specimens for RSV with reverse transcriptase polymerase chain reaction (RT-PCR) assays and paired-sera from a subset of patients with IgG enzyme immunoassay. Rates were adjusted for enrollment.

Results: Among 11,097 enrolled patients, 987 (8.9%) had RSV infection. Rates of hospitalized RSV infection overall (and radiographically-confirmed pneumonia) were highest among children aged<1 year: 1,067/100,000 (534/100,000 radiographically-confirmed pneumonia) and 1-4 year: 403/100,000 (222/100,000), but low among enrolled adults aged≥65 years: 42/100,000. Age<1 year (adjusted odds ratio [aOR]=13.2, 95% confidence interval [CI] 7.7, 22.5) and 1-4 year (aOR=8.3, 95% CI 5.0, 13.9) were independent predictors of hospitalized RSV infection.

Conclusions: The incidence of hospitalized RSV lower respiratory tract illness among children<5 years was high in rural Thailand. Efforts to prevent RSV infection could substantially reduce the pneumonia burden in children aged<5 years.

Figure 1. Adjusted annual incidence of hospitalized RSV respiratory illness (A) and hospitalized chest radiograph-confirmed RSV pneumonia (B) by age group, SaKaeo and Nakhon Phanom Provinces, during four consecutive years, January 1, 2004 – December 31, 2007.

2004 data are only from Sa Kaeo Province. Inset shows adjusted incidence values for age groups, 5–19 years, 20–49 years, 50–64 years, and ≥65 years.

Figure 2. The percentage of patients with RSV infections per total patients tested by month and year among enrolled patients from SaKaeo (solid black line) and Nakhom Phanom (solid blue line) Provinces, September 1, 2003 – December 31, 2007.