The virus affects most children before the age of two
A virus that causes wheezing and pneumonia claims the lives of up to 200,000 children worldwide each year, a study has found.
University of Edinburgh scientists found that about 3.4 million children were hospitalised after contracting respiratory syncytial virus (RSV).
RSV is the single largest cause of lung infection in children.
The scientists hope the research will help contribute to the development of a vaccine against the infection.
The study, which has been published in The Lancet, confirmed that RSV - which infects most children before the age of two - usually causes mild cold-like symptoms, but can lead to serious illness in babies who are born prematurely or who have congenital heart disease.
It is the first time that the numbers of children dying globally from RSV before the age of five have been quantified.
The international team analysed unpublished data from developing countries as well as all the published medical research on RSV infection.
They found that about 33.8 million children become infected with RSV each year and that 99% of RSV-related deaths occur in developing countries.
The team hopes that by identifying the numbers affected by the virus, it can contribute to the development of a vaccine against the infection.
Dr Harish Nair, of the University of Edinburgh's department of population health studies, said: "Our greatest hope of fighting this virus is to develop a vaccine, but before we can implement an immunisation programme, we need to understand exactly how big a problem RSV poses.
"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."
Professor Warren Lenney, spokesman for the British Lung Foundation, the only charity helping people with all lung diseases, said: "Acute Viral Bronchiolitis (RSV) is a respiratory virus which is not well known, however it is the most common reason for tiny babies to be admitted to hospital within the first year of life - across England and Wales RSV causes 20,000 babies to be admitted to hospital each year during the winter months."
He welcomed the research as indicating the size of the problem on a global scale.
"RSV not only causes respiratory problems in early life but can lead to other long-term chest problems well into teenage years," the professor added.