CIENCIASMEDICASNEWS: Ahead of Print - Respiratory Syncytial Virus Seasonality, Beijing, China, 2007–2015 - Volume 25, Number 6—June 2019 - Emerging Infectious Diseases journal

During July 2007–June 2015, we enrolled 4,225 hospitalized children with pneumonia in a study to determine the seasonality of respiratory syncytial virus (RSV) infection in Beijing, China. We defined season as the period during which >10% of total PCRs performed each week were RSV positive. We identified 8 distinctive RSV seasons. On average, the season onset occurred at week 41 (mid-October) and lasted 33 weeks, through week 20 of the next year (mid-May); 97% of all RSV-positive cases occurred during the season. RSV seasons occurred 3–5 weeks earlier and lasted ≈6 weeks longer in RSV subgroup A–dominant years than in RSV subgroup B–dominant years. Our analysis indicates that monitoring such RSV-subgroup shifts might provide better estimates for the onset of RSV transmission. PCR-based tests could be a flexible or complementary way of determining RSV seasonality in locations where RSV surveillance is less well-established, such as local hospitals throughout China.

Respiratory syncytial virus (RSV) is a major cause of lower respiratory tract infection in young children worldwide (1–3); 2.7–3.8 million hospitalizations and 94,600–149,400 deaths occur each year among children <5 years of age as a result of RSV infection (4). Studies have also demonstrated the contribution of RSV to respiratory tract infections in adults (5,6). However, no licensed RSV vaccine is available (7), and the only approved specific therapy, palivizumab (anti–RSV antibody), has limited uses among infants at high risk for severe respiratory illness in high-resource settings (8).

RSV causes epidemics in the winter in regions with temperate climates (8,9). However, spatiotemporal variations have been observed in the timing of RSV activity (10,11), and knowledge of the exact timing is helpful for guiding healthcare providers and health officials on the timing of diagnostic testing and immunoprophylaxis for infants at high risk for infection (12). RSV circulation is monitored in the United States year-round through the National Respiratory and Enteric Virus Surveillance System (10) and in 15 countries of Europe through the European Influenza Surveillance Network (13). Since 2017, the World Health Organization has also conducted RSV surveillance to guide its global RSV prevention strategy (9) using the Global Influenza Surveillance and Response System (14). However, most of the real-time data on RSV seasonality comes from RSV surveillance, and data are lacking in many places of the world. Because disease surveillance is labor- and resource-intensive, information on seasonality from other sources is needed.

China has a high burden of RSV infection (4), but RSV surveillance in this country is less established, and implementation of diagnostic tests is limited. Several previous studies reported an RSV prevalence of 17%–33% among children with severe acute respiratory illness (15,16), but few have assessed the seasonality or trends of RSV infections in China. Not having data available on RSV seasonality in China could encumber implementation of therapy and prophylactic interventions for RSV.

Since July 2007, we have been monitoring for RSV infection among hospitalized children with pneumonia in Beijing, China. In this study, we evaluated the PCR results collected in 8 consecutive years (2007–2015) to characterize the seasonality of RSV by year. Also, because disease and death attributable to RSV varies from year to year (4,11,17), we explored the factors that might affect RSV activity.