MARSEILLE, France – It is well known that viral infections, especially respiratory syncytial virus (RSV) and rhinovirus (RV), exacerbate symptoms of asthma. But could they also play a part in triggering the onset of asthma?
The link between RSV and RV infections in early childhood and the development of asthma symptoms is well established, said Camille Taillé, MD, PhD, of the department of respiratory medicine and the rare diseases center of excellence at Bichat Hospital, Paris. But getting asthma is probably not just a matter of having a viral infection at a young age or of having a severe form of it. Gene polymorphisms, immune system disorders, and preexisting atopy are also associated with the risk of asthma. This was the focus of the 27th French-language respiratory medicine conference, held in Marseille, France.
RV and RSV
Persons with asthma are vulnerable to certain viral respiratory infections, in particular the flu and RV, which can exacerbate asthma symptoms. Inhaled corticosteroids have an overall protective effect against viral-induced exacerbations. For worsening asthma symptoms during an epidemic or pandemic, there is no contraindication to inhaled or oral corticosteroids.
Young children from the time of birth to 4 years of age are particularly susceptible to viral respiratory infections. According to data from France’s clinical surveillance network, Sentinelles, from the period covering winter 2021-2022, the rate of incidence per 100,000 inhabitants was systematically greater for the 0 to 4-year age range than for older age ranges.
Of the most common viruses that infect young children, RV, the virus that causes the common cold, is a nonenveloped RNA virus from the enterovirus family. There are 160 types, which are classified into three strains (A, B, and C). Of those strains, A and C confer the most severe infections. The virus is highly variable, which makes developing a vaccine challenging. The virus circulates year round, usually peaking in the fall and at the end of spring. RSV is an RNA virus that is classed as a respiratory virus. It comprises two serotypes: type A and B. Almost all children will have been infected with RSV by the time they are 2 years old. Epidemics occur each year during winter or in early spring in temperate climates. Vaccines are currently being developed and will soon be marketed. A monoclonal antibody (palivizumab), which targets fusion proteins of the virus, is available as prophylactic treatment for at-risk children.
RSV infection
During an RSV infection, the severe inflammation of the bronchial and alveolar wall causes acute respiratory distress. “But not all infants will develop severe forms of bronchiolitis,” said Dr. Taillé. “The risk factors for the severe form of the illness are well known: being under 6 months of age, prematurity, comorbidities (neurovascular, cardiovascular, respiratory, etc.), history of a stay in a neonatal intensive care unit at birth, living in low socioeconomic status towns, and exposure to smoking.”
Asthma development
The issue of whether or not viral diseases cause asthma has been the subject of intense debate. The studies are starting to stack up, however. They seem to show that RSV or RV infections are associated with the risk of subsequent asthma development. “For example, in a study published in 2022,” said Dr. Taillé, “in children admitted with an RSV infection, 60% of those who had been admitted to neonatal intensive care presented with symptoms of asthma between 3 and 6 years of age, compared with 18% of those who had had a milder case of RSV (admitted to nonintensive care settings). A serious RSV infection is a risk factor for later development of asthma.”