Respiratory Syncytial Virus (RSV) is a highly common respiratory illness that circulates seasonally, typically causing mild, cold-like symptoms in older children and adults. For infants, however, this virus can lead to serious lower respiratory tract infections such as bronchiolitis and pneumonia. Nearly all children will have contracted RSV by the time they reach two years of age. This analysis provides data on the burden of this illness in the United States, specifically addressing the mortality and morbidity rates among infants.
Understanding the Scope of RSV Mortality in US Infants
RSV represents a considerable burden on the healthcare system and is recognized as the leading cause of hospitalization for infants under one year old in the United States. Each year, an estimated 58,000 to 80,000 children younger than five years old are hospitalized due to complications from the virus, with the majority occurring in infants. Research suggests that between 79,850 and 86,020 RSV-associated infant hospitalizations occur annually, underscoring the virus’s ability to cause severe illness. For infants under six months of age, two to three out of every 100 will require hospitalization during an RSV season.
The number of deaths directly attributed to RSV in infants remains relatively low. A study analyzing data from 1999 to 2018 found an average of approximately 28 RSV-associated deaths in infants annually. Tracking the total number of deaths is difficult because the virus can lead to other complications, like bacterial pneumonia, which may be listed as the primary cause of death. Recent analyses suggest the annual number of RSV-associated deaths in children under five years old is likely 510 or fewer.
Factors That Increase Severe Risk
While most infants experience a mild case of RSV, certain factors significantly increase the risk of severe disease, hospitalization, or death. The single greatest medical risk factor is being born prematurely, as these infants have underdeveloped lungs and immune systems. Infants born before 32 weeks of gestation are at a substantially higher risk for severe complications.
Age is a major determinant of severity, with infants under six months old being the most vulnerable population. Their small airways are more easily obstructed by the inflammation and mucus caused by the infection, leading to breathing difficulties. Children with underlying health conditions also face a heightened risk of severe illness. These conditions include chronic lung disease, such as bronchopulmonary dysplasia (BPD), and congenital heart disease. A compromised immune system, due to a medical condition or medication, limits a baby’s ability to fight off the infection, increasing the likelihood of a severe outcome. Some data also shows that American Indian and Alaska Native children experience higher rates of RSV-associated hospitalization compared to other groups.
Recognizing Severe RSV Symptoms
RSV typically begins with symptoms resembling a common cold, such as a runny nose, sneezing, and a mild cough. The transition to a severe infection often occurs within a few days when the virus spreads to the lower respiratory tract, resulting in bronchiolitis or pneumonia. Recognizing the signs of respiratory distress is important for seeking prompt medical care.
A primary indicator of severe RSV is a change in breathing patterns, which may become rapid, shallow, or labored. Parents should look for retractions, which are visible signs of the chest wall or skin between the ribs being pulled inward with each breath. Wheezing, a high-pitched whistling sound often heard during exhalation, indicates inflammation and narrowing of the small airways.
In very young infants, symptoms can be less specific and may include increased irritability, decreased activity, or a refusal to feed. A sign of dangerously low oxygen levels is cyanosis, a bluish discoloration around the mouth, lips, or fingernails, which requires immediate emergency intervention. Any infant exhibiting these severe symptoms, or struggling to maintain hydration due to poor feeding, should be evaluated by a healthcare provider without delay.
Protecting Infants from RSV
Protection against severe RSV involves a combination of medical interventions and general hygiene practices. Two medical advancements have been introduced to provide passive immunity to infants.
Medical Interventions
One strategy is the administration of a maternal RSV vaccine, such as Abrysvo, given to pregnant individuals between 32 and 36 weeks of gestation. This vaccine allows protective antibodies to pass from the parent to the fetus, offering immunity during the baby’s first months of life. Another option is the monoclonal antibody injection, Nirsevimab (Beyfortus), which provides a full season of protection from a single dose. This product is recommended for all infants under eight months old entering their first RSV season. For infants at high risk, a monthly monoclonal antibody product called Palivizumab (Synagis) may be prescribed during the RSV season.
General Hygiene Practices
Beyond medical options, general environmental measures are important for reducing exposure to the virus. Frequent hand washing with soap and water for at least 20 seconds is an effective defense against the virus, which can live on surfaces for several hours. Limiting an infant’s exposure to sick individuals and avoiding crowded settings during peak RSV season can reduce the risk of infection. Additionally, infants should not be exposed to secondhand smoke, as it can worsen respiratory symptoms and increase the risk of severe illness.