Although it usually causes only mild cold-like symptoms, the virus in premature infants or those who have congenital heart disease can cause serious illness, University of Edinburgh said.
An international team of researchers analyzed data from developing countries and all the published studies on RSV and found more than 33.8 million children get infected with RSV each year.
The study, published in The Lancet, found 99 percent of RSV-related deaths occur in developing countries.
"Our greatest hope of fighting this virus is to develop a vaccine, but before we can implement an immunization program, we need to understand exactly how big a problem RSV poses," Dr. Harish Nair of the University of Edinburgh said in a statement.
"This is the first time we have gathered information on such a global scale and is the best estimate we have for the number of children dying each year from this preventable illness."