Respiratory Syncytial Virus (RSV) is a widespread respiratory pathogen that causes infections of the lungs and respiratory tract. It is a common cause of respiratory illness, especially during specific periods of the year. RSV circulates globally, contributing to a significant burden of disease across different age groups.
Prevalence and Risk Groups
RSV is highly common, with nearly all children experiencing an infection by their second birthday. Globally, it causes an estimated 3.6 million hospitalizations and around 100,000 deaths annually in children under five years of age. Approximately half of these pediatric deaths occur in infants under six months old.
Beyond young children, RSV also affects older adults and individuals with compromised immune systems or underlying health conditions. For adults aged 65 and older, the virus can result in 60,000 to 160,000 hospitalizations annually in the U.S.
RSV infections typically follow seasonal patterns. In temperate climates, such as most of the United States, outbreaks tend to occur in the late fall and winter, with elevated viral circulation lasting about five months. While tropical and subtropical regions may not have such sharply defined seasonality, they still experience consistent months of high RSV circulation each year.
Impact and Outcomes
For many healthy individuals, RSV infection causes mild, cold-like symptoms such as a runny nose, coughing, sneezing, and fever. These symptoms usually resolve on their own within a week or two. However, the virus can lead to more severe outcomes, particularly in vulnerable populations.
In infants and young children, RSV is the primary cause of bronchiolitis, an inflammation of the small airways in the lungs, and pneumonia, a lung infection. Approximately 2-3% of children experiencing their first RSV infection in the first year of life require hospitalization. In industrialized countries, mortality in previously healthy children hospitalized for bronchiolitis is low, typically ranging from 0-1.5%, due to access to mechanical ventilation and intensive care.
Adults, especially those over 65, and individuals with underlying conditions like asthma, chronic obstructive pulmonary disease (COPD), or congestive heart failure, face a higher risk of severe RSV disease. In the U.S., RSV is estimated to cause up to 10,000 deaths annually among adults over 65. The risk of serious outcomes in adults aged 60 and above is at least double for those with COPD or congestive heart failure compared to individuals without these conditions.