Infant mortality rates for RSV much lower than previously thought

It's a virus that has long been characterized as dangerous and even deadly, but new research shows infant deaths from respiratory syncytial virus (RSV) are actually quite uncommon in the 21st century.

Researchers at the University of Utah have shown there are approximately 42 deaths annually associated with RSV in the United States, and of those deaths, the majority are in infants and young children that have complex preexisting chronic conditions.

"The news is very good for parents and their babies," says Carrie Byington, M.D., professor of pediatrics at the University of Utah and the study's principal investigator.

In most children, RSV will present with cold symptoms such as a runny nose, cough, wheezing, and mild fever. It can often lead to bronchiolitis (a swelling of the airways which makes breathing difficult) and pneumonia. In babies younger than six months, these conditions may require hospitalization. "Although RSV is one of the most common causes for infant hospitalizations, we can support infants through this infection. Most hospitalizations will be 2-3 days with infants expected to recover fully," Byington said.

Most babies can handle the virus and these symptoms, but those at higher risk for serious complications include very premature babies with lung disease and those born with heart problems or immune deficiencies.

The study, published today in the journal Pediatrics, determined mortality rates are much lower than previously thought. Based on research from decades ago, estimates showed RSV was linked to 210 - 4,500 deaths annually. The new study estimates the annual death toll to be up to 100-fold lower based on analysis of two national databases representing more than 850,000 RSV-associated admissions between the years 2000 to 2011. The decrease in mortality is likely the result of advances in medical care since the first estimates were calculated.

This new information may help guide appropriate prevention and treatment strategies. For example, medication that helps prevent RSV hospitalizations is very costly. "The use of these medications has been controversial," says Byington. "This research may help guide more appropriate use of these costly medications for the infants and young children most at risk for developing severe complications," she said.

The information may also help focus research, such as targeting preventative vaccines to the subset of children most at risk for complications from RSV.