RSV Season 2023

A study published by the Journal of Infectious Diseases determined that respiratory syncytial virus (RSV)-related deaths in infants <1 year peaked at one month, while bronchiolitis and influenza mortality peaked at two months. Over the 20-year study period, RSV, bronchiolitis, and influenza were listed as the underlying causes of death on 932, 1,046, and 52,293 death certificates, respectively. Children <1 year of age accounted for 39% of RSV and bronchiolitis deaths. Over 95% of these infections in children occur in low- and middle-income countries outside the U.S.

The U.S. Centers for Disease Control and Prevention (CDC) Morbidity and Mortality Weekly Report, published on April 7, 2023, presented the seasonality of RSV in the U.S. from 2017–2023. The 2022–23 RSV season started later than the 2021–22 season but earlier than the prepandemic seasons, suggesting a return toward prepandemic seasonality. Previously, the U.S. CDC's Natalie J. Thornburg, Ph.D., presented information on RSV virology, strain variation, and surveillance measures on February 28, 2023. Across both prepandemic and pandemic years, RSV circulation in the U.S. began in Florida, then the southeast, and later in the north and west regions.

RSV Seaonality Florida 2023

Florida's RSV season is longer than the rest of the U.S. and has distinct regional patterns. For this reason, the state is segmented into five RSV regions, each with its season. The Florida Department of Health established regional RSV seasons based on activity thresholds provided by the CDC. As of May 14, 2023, RSV activity was low.

RSV Seasonality in the Americas

The Pan American Health Organization (PAHO) published on May 23, 2023, an updated Protocol and Technical note regarding RSV laboratory diagnosis. And the seasonality of RSV in Latin America and the Caribbean is updated by SARInet. As of Week #18 of 2023, RSV activity has remained low throughout most of the Americas.

RSV Global

The WHO Influenza Update N° 445, published on May 15, 2023, disclosed RSV activity globally was generally low except in Australia and a few countries in the Region of the Americas. However, RSV remained elevated in Guatemala and increased in several countries in tropical and temperate South America.

RSV Influenza Comparison

The JAMA Network published an Original Investigation on February 28, 2022: Mortality Associated With Influenza and Respiratory Syncytial Virus in the U.S., 1999-2018. This study suggests that RSV poses a greater risk than influenza to infants, while both are associated with substantial mortality among elderly individuals. Influenza has sizeable interannual variability, affecting different age groups depending on the circulating virus. A mean of 6549 (95% CI, 6140-6958) underlying respiratory deaths was associated with RSV annually, including 96 (95% CI, 92-99) deaths among children younger than one year. For influenza, there were 10 171 (95% CI, 9652-10 691) underlying respiratory deaths per year, with 23 deaths (95% CI, 19-27) among children younger than one year.

A study published in 2017 found that adult patients were less likely to be diagnosed with RSV than with influenza (2.3 vs. 8.3%, respectively), were older, and were more likely to be diagnosed with pneumonia, chronic obstructive pulmonary disease, hypoxemia, and bacterial co-infection. Furthermore, in patients with RSV infection, the 20-day all-cause mortality was higher than that for influenza (18.4 vs 6.7%, respectively). In addition, RSV infection showed a significantly higher risk of death than the seasonal influenza group, with a hazard ratio of 2.32 (95% CI, 1.17–4.58).