Incidence of Respiratory Syncytial Virus Lower Respiratory Tract Infections During the First 2 Years of Life: A Prospective Study Across Diverse Global Settings

Abstract

Background: The true burden of lower respiratory tract infections (LRTIs) due to respiratory syncytial virus (RSV) remains unclear. This study aimed to provide more robust, multinational data on RSV-LRTI incidence and burden in the first 2 years of life.

Methods: This prospective, observational cohort study was conducted in Argentina, Bangladesh, Canada, Finland, Honduras, South Africa, Thailand, and United States. Children were followed for 24 months from birth. Suspected LRTIs were detected via active (through regular contacts) and passive surveillance. RSV and other viruses were detected from nasopharyngeal swabs using PCR-based methods.

Results: Of 2401 children, 206 (8.6%) had 227 episodes of RSV-LRTI. Incidence rates (IRs) of first episode of RSV-LRTI were 7.35 (95% confidence interval [CI], 5.88-9.08), 5.50 (95% CI, 4.21-7.07), and 2.87 (95% CI, 2.18-3.70) cases/100 person-years in children aged 0-5, 6-11, and 12-23 months. IRs for RSV-LRTI, severe RSV-LRTI, and RSV hospitalization tended to be higher among 0-5 month olds and in lower-income settings. RSV was detected for 40% of LRTIs in 0-2 month olds and for approximately 20% of LRTIs in older children. Other viruses were codetected in 29.2% of RSV-positive nasopharyngeal swabs.

Conclusions: A substantial burden of RSV-LRTI was observed across diverse settings, impacting the youngest infants the most. Clinical Trials Registration. NCT01995175.

Keywords: burden of disease; epidemiology; incidence; infants; respiratory syncytial virus; respiratory tract infections; young children.

Graphical Abstract

Figure 1.

Participant flowchart and local RSV transmission period. The RSV transmission period in each country was defined based on the actual observed RSV season during the period of surveillance for each country. For countries such as Canada, the Unites States, and Finland, which had well-established RSV surveillance systems in place near the study sites, the actual reported RSV season start and stop dates (by month) were used to define the RSV transmission period. If the RSV season was longer in 1 year than the other and >5% of children for that country were exposed to the longer season, then the longer season was considered. In countries without a robust RSV surveillance system, the RSV transmission period was established through the identification of at least 1 RSV case in each month defined as being within the RSV season. In order for the month to be counted as within the RSV season for that country, the month had to be adjacent to at least 1 other month that similarly met the definition for being within the RSV season. Abbreviation: RSV, respiratory syncytial virus.

Figure 2.

Incidence rate of first episode of RSV-LRTI (A), severe RSV-LRTI (B), and RSV hospitalization (C) by age group, overall, and by country. Error bars represent 95% CIs. Abbreviations: CI, confidence interval; IR, incidence rate (cases/100 person-years); LRTI, lower respiratory tract infection; RSV, respiratory syncytial virus.

Figure 3.

Virus codetection in laboratory-confirmed RSV-LRTI cases (left) and according to RSV subtype (right), by age group, overall, and by country. Abbreviations: LRTI, lower respiratory tract infection; RSV, respiratory syncytial virus. ^aNo LRTIs were observed in these age groups.