More than 2 million children with Respiratory Syncytial Virus (RSV) are seen in hospitals, emergency rooms and doctors' offices in the United States every year -- many more than doctors know. In fact, only 3 percent of children with RSV in an outpatient setting actually receive a diagnosis of RSV infection.
Although attention is focused on young babies and those with high-risk medical conditions, more older children who were previously healthy need medical attention from RSV infections. Of the 2.1 million children younger than 5 years of age with RSV infection, 78 percent of them are older than 12 months, according to a University of Rochester Medical Center published in this week's New England Journal of Medicine.
Most children with RSV infections, both those who were hospitalized and those who were treated in doctors' offices, had no other medical conditions or high-risk characteristics that significantly identified them as being at greater risk for severe RSV disease, except for being younger than 2 years of old.
"We have been focused primarily on high-risk infants under a year old with RSV, but this study shows that an unrecognized and large burden exists among children with no risk factors and who are between 1 and 5 years old," said Caroline Breese Hall, M.D., professor of Pediatrics and Medicine at the University of Rochester Medical Center and author of the study. "The rates of RSV infections requiring medical attention are high not only during infancy but throughout the first 5 years of life. This factor underscores the as-yet-unmet need for an effective vaccine."
The study also found that most of the burden of RSV comes from children seen in doctors' offices -- 73 percent, compared to 25 percent seen in emergency departments and about 3 percent who are hospitalized
Furthermore, the children seen in the doctors' offices are generally quite ill. "About three-fourths have labored breathing (or are having difficulty breathing), which is similar to the proportion of children with RSV who are sent to the emergency department.," Hall said.
RSV is highly contagious. All children are infected with RSV during their first two years of life and may be repeatedly infected thereafter, sometimes within months. This study found that RSV causes three times as many hospitalizations as does influenza and parainfluenza in children under 5 years of age.
The study, which was performed as part of the CDC-funded New Vaccine Surveillance Network, was a prospective, population-based surveillance of acute respiratory infections among children younger than 5 in hospitals, emergency rooms and pediatric offices in Rochester, NY, Nashville, TN, and Cincinnati, Ohio, between 2000 and 2004. Among the 5,067 children enrolled in the study, 18 percent (919) had RSV infections. Only prematurity and a young age were independent risk factors for hospitalization, but prematurity was also a risk factor for hospitalization with any type of respiratory infection.. The study estimates that among children under the age of 5 years, RSV infection results in about 1 of 334 hospitalizations, 1 of 38 visits to an emergency department, and 1 of 13 visits to a primary care office each year in the United States.
Hall has consulted for MedImmune, which makes Synagis, a monoclonal antibody. It is used to prevent viral respiratory tract infections (RSV infection) in infants and young children at risk for infection.