The annual RSV (respiratory syncytial virus) epidemic, which spreads between December and February-March, infects hundreds of infants with bronchiolitis, an inflammation of the smallest airways in the lungs. As a result, the child’s risk of developing asthma increases. There are no vaccines or medicines against the virus. Professor Matti Korppi from the University of Tampere leads the most long-standing research on the consequences and causes of bronchiolitis in the world.
The course of the disease varies a lot – in some patients it is milder and some have a more severe infection. Some patients must be treated in hospitals because they have difficulties breathing.
In the Nordic countries, RSV bronchiolitis is currently considered an infection affecting 0-6-month-old babies because they present with the most typical clinical picture. In the rest of Europe, bronchiolitis is considered a disease of infants who are younger than 12 months. In the United States, the age limit is thought to be two years, which makes it difficult to compare European and North American research results.
The most long-standing follow-up study started in 1981
Korppi started to study respiratory infections caused by RSV in Kuopio in 1981. That first cohort is still being followed up and so is also the second cohort study, which he started in Kuopio in 1992.
As professor of paediatrics at the University of Tampere, Korppi has continued his study, which gathered a group of 0-6 month-old patients in 2000-2004. These children were investigated for a second time at the age of twelve in the summer of 2014, and the results from this study are currently being analysed.
There are only five similar longitudinal studies in the world. Apart from the Finnish studies, such studies have been conducted in Gothenburg and Malmö in Sweden where the patients have been followed for up to twenty years.
Bronchiolitis in babies is most often caused by RSV, but other viruses may also play a role. Risk factors for later asthma include the baby’s allergy, the mother’s asthma and the parents’, especially the mother’s, smoking.
“The study on the cohort gathered in Tampere concentrated on genetic causes. Is the regulation of innate immune responses the reason why some patients are more prone to severe forms of the disease, which require treatment in hospital, and why they have a higher risk of developing asthma?” Korppi asks.
RSV raises the child’s risk of developing asthma two or threefold compared with the rest of the population. The study Korppi conducted in Kuopio established for the first time in the world that if the most common virus causing a head cold in adults, the rhinovirus, causes shortness of breath in the baby, they have even a tenfold risk of developing asthma later.
Large datasets are needed in genetic research and the longitudinal follow-up studies from Kuopio, Tampere and Gothenburg cooperate with longitudinal studies conducted for five and six years in Turku in Finland and Utrecht in the Netherlands.
“The whole genome has been mapped in these data and its statistical analysis is now being conducted at the University of Oulu,” Korppi says.
RSV is one of a kind and there is no vaccine
“The problem with bronchiolitis is that most of the infections are caused by that one virus, which spreads in the population once a year and which almost all people catch,” Korppi says.
“All other such diseases in human history have been conquered by vaccines, and this is the only virus left without vaccinations that goes around the world causing large epidemics. Researchers have so far been unable to develop a vaccine against RSV even though they have worked very hard to do so.”
Bronchiolitis is difficult to treat because none of the current medicines work. “We have tried both asthma therapies and cortisone, which did not work. At one time there was a medicine, which in principle killed the virus, but it is no longer used as it did not prove efficient enough.”
A new treatment found in high flow oxygen?
The only thing that clearly helps is giving the babies oxygen if the oxygen level in their blood stream declines, and taking good care of nourishment – the babies should get enough fluids even when they are too weak to suck.
“The latest promising therapy is high flow oxygen administered with a small amount of positive pressure,” Korppi says.
This therapy is already being used in some Australian hospitals, for example, but as yet there are no proper studies about it. Korppi is about to start investigating the method in cooperation with colleagues at the University of Oulu.
“If the treatment proves to be helpful, it would make sense to use it to treat bronchiolitis in hospitals,” Korppi says.
“The aim is to lower the threshold of starting this treatment and to avoid placing the babies in intensive care and having to use ventilators.”
Text: Pirjo Achté