Viral Respiratory Tract Infections in Young CF Children Usually Mild, Study Found

Viral respiratory tract infections in young children with cystic fibrosis tend to be mild and not require hospitalization, a study found.

Infections caused by respiratory syncytial virus (RSV) were rare and did not lead to complications, suggesting that there is no need for preventive medication such as Synagis (palivizumab) in this young population.

The study, “Viral respiratory tract infections in young children with cystic fibrosis: a prospective full-year seasonal study,” was published in Virology Journal. 

Bacteria are considered the leading cause of respiratory tract infections in young children with CF, but viral infections also are common. RSV can cause severe infection in some patients, in which the virus can spread to the lower respiratory tract, causing pneumonia or bronchiolitis — inflammation of the small airway passages entering the lungs.

Studies performed in the 80s and 90s reported that viruses, especially RSV, caused severe infections, usually requiring hospitalization. However, the diagnostic tools at that time were limited, and those results may not be accurate.

A recent study showed that viral infections increased the risk of bacterial infections and airway inflammation in infants with CF. However, the impact of viral infections on the course of the disease remains unknown.

Now, researchers in France performed a prospective study to determine the frequency of viral respiratory tract infections, and how they impacted the short-term outcomes in young children with CF.

The investigators used recently developed, more accurate diagnostic tools to identify the viruses causing the infections. The study included 25 children younger than 2 years (mean age of 9.6 months), who had not previously taken Synagis.

During the course of one year, nasal swabs were taken from each child every month or every two months, depending on the season. Additional swabs were taken if the child had symptoms of respiratory tract infection.

The children had, on average, 3.4 respiratory tract infections per year, 1.8 of which were caused by viruses.

Overall, 69% of the samples collected in children with symptoms of infection tested positive for at least one respiratory virus — as did 33% of the samples from children with no signs of infection.

The most common were rhinovirus — the virus that causes the common cold — and enterovirus, present in 61% of the positive samples. This was followed by RSV, which was present in 14% of the samples.

Researchers noted that the children infected with RSV were few, and “none required hospitalization.”

“Even in the youngest patients, the clinical course was uncomplicated,” the investigators said.

“These findings contrast with those reported decades ago in unscreened CF babies in whom RSV infection was described as severe,” they said. “The overall better health status of the children with CF in the present sample is likely the main explanation for this result, as well as their older age at the time of RSV infection.”

Five children required hospitalization during the study, one due to viral infection (rhinovirus/enterovirus), and four due to other causes.

Participants who got bacterial infections during the study tended to have more severe symptoms of respiratory tract infection, but the difference was not statistically significant.

Most patients (86%) received antibiotics during the study, and those who had more symptoms of respiratory tract infections took antibiotics for more days.

Overall, the team concluded that “respiratory viruses are responsible for around two-thirds of RTIs [respiratory tract infections] in young children with CF.”

“Viral RTIs are usually of mild severity, exceptionally leading to hospitalization. RSV infections were rare, and this raises the question of the usefulness of RSV preventive medication in this young population,” they added.