Pediatric Patients at Increased Risk of Respiratory Syncytial Virus Infection

Laura Bubba, PhD

Investigators from Italy performed a sentinel surveillance of influenza-like illness, which identified patient populations who were at higher risk of respiratory syncytial virus (RSV) and influenza infection.

From there, investigators led by Laura Bubba, PhD, Department of Biomedical Sciences for Health, University of Milan, were able to define the start, duration, timing, and intensity of the RSV and influenza community circulation.

Bubba and colleagues noted that respiratory syncytial virus has been a major cause of lower respiratory tract illness in young children and can also result in influenza-like illness.

As such, they investigated the epidemiological features of respiratory syncytial virus in pediatric patients with influenza-like illness in the region of Lombardy from 2014-2015 to 2020-2021 winter seasons.

The Methods

In order to retrieve epidemiological and virological data on the region of Lombardy, Bubba and colleagues utilized surveillance data from the Italian influenza surveillance network (InfluNet).

The intention of InfluNet has been to track influenza epidemics across Italy, in addition to detecting their starting point, monitoring their spatial-temporal spread, identifying populations at risk and circulating influenza viruses, as well as estimating the impact on the community and healthcare structures.

For this study, the influenza-like illness case definition was done in accordance to the European Center for Disease Prevention and Control (ECDC), which consisted of an abrupt onset of fever (>38C) or feverishness, 1 or more respiratory symptoms (cough, sore throat and/or shortness of breath) and 1 or more systemic symptoms such as myalgia, headache or malaise.

Investigators collected epidemiological surveillance data on aggregate consultations of influenza-like illness, age and gender, date of symptoms onset, influenza vaccination status, and the presence or absence of pre-existing underlying health conditions.

The Findings

Bubba and colleagues observed that the cumulative incidence of influenza-like illness cases in the general population ranged from 5% in 2020-2021 to 16.2% in 2017-2018.

In all seasons, the highest cumulative incidence of ILI cases was reported in the 0–4 years age group (mean: 22.7%, range: 7.7%–43.6%), followed by the 5–14 years age group (mean: 13.4%, range: 3.2%–21.0%). A decrease was observed in the adult group (15-64 years) and in the ≥65 years age group (mean: 4.6%, range: 2.0%–7.4%).

A total of 3971 nasopharyngeal swabs were collected in the seven winter seasons included in the study. Excluding the 2020–2021 winter season the mean positivity rate for influenza virus was 51.0% (ranging from 31.2% in 2019–2020 to 63.8% in 2017–2018) compared to 13.2%. for respiratory syncytial virus.

Overall, respiratory syncytial virus made for nearly 19% of pediatric influenza-like illness, with an infection risk that was nearly 2 times greater than that of patients 15 years and older.

However, the age groups 4-6 months and 7-12 months showed a 5-fold greater risk of infection from respiratory syncytial virus than from influenza, and children ≤5 years of age with pre- existing underlying health conditions had a nearly 5-fold greater risk of getting a respiratory syncytial virus infection than otherwise healthy 0–5 years old children.

Investigators believed the data revealed sentinel surveillance to be a valuable asset in defining respiratory syncytial virus circulation and aided in identifying groups at higher risk fo infection.

“The extension of virological surveillance to RSV and other respiratory viruses should be implemented within ILI surveillance to assess their circulation and impact in a real-time manner,” the team wrote.

The study, “Respiratory syncytial virus in pediatric influenza-like illness cases in Lombardy, Northern Italy, during seven consecutive winter seasons (from 2014–2015 to 2020–2021),” was published online in Influenza.