Asthma could be prevented by giving women a simple jab during pregnancy to protect their child from a common chest infection, say scientists.
Bronchiolitis affects up to half of babies and can increase their risk of developing the chronic condition five-fold, according to new research.
It is triggered by a virus called RSV that causes the lungs to become inflamed.
Infants admitted to hospital with the chest infection are much more likely to need emergency treatment for asthma – before they reach school age, the study found.
The findings offers hope of protecting babies – even while they are still in the womb.
Lead author Dr Helen Skirrow, from the School of Public Health at Imperial College London, explained: “There are a number of trials underway at the moment developing an RSV vaccine that could either be given to newborns or pregnant women.
“This work provides more evidence of the importance of investing in this research, and the effect it could have on children’s long-term health.”
Bronchiolitis is so infectious because RSV (respiratory syncytial virus) multiplies very quickly, causing the smallest airways in the lungs, the bronchioles, to become inflamed.
This reduces the amount of air entering, making it difficult for babies to breath.
Symptoms also include fever, cough and wheezing.
Now Dr Skirrow and colleagues have linked serious cases to asthma, wheezing and respiratory illness.
The bug is so prevalent it sometimes bring hospitals to a standstill during winter.
Most cases are mild and clear up within two to three weeks. But some cases are severe.
The findings are based on 613,377 babies – almost all births in England between April 2007 and March 2008 – who were tracked up to the age of five.
Bronchiolitis usually strikes infants when they are between three and six months old.
The 16,000 admitted to hospital for it before their first birthday were up to five times more likely to have emergency treatment for asthma, wheezing or respiratory illness.
The researchers also found one in five children admitted to hospital with bronchiolitis as a baby will have a subsequent emergency hospital admission for asthma, wheeze, or respiratory infections.
Dr Skirrow said: “We know that hospital admissions for bronchiolitis have been rising over recent years in England.
“Previous studies have suggested a link between the condition and an increased risk of conditions such as asthma, but this is the largest study to suggest a severe case of bronchiolitis can result in subsequent emergency admissions for asthma and other respiratory conditions. ”
She added: “An emergency hospital admission is incredibly stressful for children and their families, and also places a burden on hospitals.
“If we develop interventions to prevent the initial bout of bronchiolitis – we may also be able to reduce the number of subsequent emergency admissions.”
Most children get better on their own. But up to one in 20 (5%) will require hospital treatment if they develop more severe symptoms, such as breathing difficulties.
The RSV bug is responsible for around 3.2 million hospital admissions every year worldwide.
Although there is no treatment for bronchiolitis, children thought to be at risk of RSV infection, such as babies born prematurely, can be given a preventative treatment called palivizumab.
There are also a number of RSV vaccines currently in development.
Many factors contribute to a baby’s risk of being admitted to hospital for bronchiolitis and other respiratory illnesses.
These include exposure to tobacco smoke inside the home, environmental factors, such as air quality, and whether a child was bottle fed rather than breast fed.
The study published in Archives of Disease in Childhood highlight the importance of preventing cases of bronchiolitis, said the team.
Senior author Professor Sonia Saxena, head of Imperial’s Child Health Unit, added: “Having your baby admitted to hospital with a serious chest infection like bronchiolitis is a frightening experience for parents.
“Our study shows these children are at high risk of subsequent hospital admission for asthma and recurrent infections across the early years of life, so we should be doing all we can to prevent this happening.
“Health professionals should counsel parents about benefits of breastfeeding, avoid infant’s exposure to tobacco smoke and raise parent’s awareness of when and how to seek help for respiratory problems as their child develops during preschool years.”
The analysis took into account infants with pre existing conditions.
The scientists say more work is still needed to investigate why bronchiolitis may be linked to subsequent respiratory problems such as asthma.
One theory is the initial viral infection that caused bronchiolitis may alter the immune system’s response, increasing the chance of subsequent asthma and wheezing.
Another is that a baby remains exposed to the initial triggers of bronchiolitis, such as second-hand smoke or pollution, which subsequently triggers asthma or other respiratory conditions.
The team say the research also highlights the need to develop a vaccine against RSV, that would stop bronchiolitis in its tracks.
This would halt the virus from replicating itself inside cells in the lining of the lungs and nose.