Seasonal and inter-seasonal RSV activity in the European Region during the COVID-19 pandemic from autumn 2020 to summer 2022

Prevalence of Co-Infections in Primary Care Patients with Medically Attended Acute Respiratory Infection in the 2022/2023 Season

In the post-pandemic period, an endemic circulation of respiratory viruses has been re-established. Respiratory viruses are co-circulating with SARS-CoV-2. We performed a retrospective analysis of co-infections in primary care patients with medically attended acute respiratory infections (MAARI) who consulted from week 40/2022 to week 39/2023 and were tested for a panel of respiratory viruses. Out of 2099 samples tested, 1260 (60.0%) were positive for one virus. In 340 samples, co-infection was detected: two viruses in 281 (13.4%), three viruses in 51 (2.4%), and four viruses in eight (0.4%) samples. Respiratory viruses co-infected the patients with MAARI at very different rates. The lowest rates of co-infections were confirmed for influenza B (13.8%) and influenza A (22.9%) and the highest for human bocaviruses (84.0%) and human parechoviruses (82.1%). Co-infections were detected in 28.2% of SARS-CoV-2 positive samples. SARS-CoV-2 has never been co-infected with influenza B virus, enterovirus or adenovirus, although the latter was found as a co-infecting virus with all other respiratory viruses tested. The rate of co-infections decreased significantly with increasing age (p-value 0.000), and no difference was found regarding gender (p-value 0.672). It is important to understand the epidemiology of respiratory co-infections for prevention and management decisions in patients with MAARI.

Nirsevimab Effectiveness Against Cases of Respiratory Syncytial Virus Bronchiolitis Hospitalised in Paediatric Intensive Care Units in France, September 2023-January 2024

In September 2023, France was one of the first countries that started a national immunisation campaign with nirsevimab, a new monoclonal antibody against respiratory syncytial virus (RSV). Using data from a network of paediatric intensive care units (PICUs), we aimed to estimate nirsevimab effectiveness against severe cases of RSV bronchiolitis in France. We conducted a case-control study based on the test-negative design and included 288 infants reported by 20 PICUs. We estimated nirsevimab effectiveness at 75.9% (48.5-88.7) in the main analysis and 80.6% (61.6-90.3) and 80.4% (61.7-89.9) in two sensitivity analyses. These real-world estimates confirmed the efficacy observed in clinical studies.

Estimated Impact of Nirsevimab on the Incidence of Respiratory Syncytial Virus Infections Requiring Hospital Admission in Children < 1 Year, Weeks 40, 2023, to 8, 2024, Spain

BACKGROUND

Data from the sentinel surveillance system of severe acute respiratory infections in Spain were used to estimate the impact of administration of nirsevimab to children born from 1 April 2023 onwards.

METHODS

Estimated RSV hospitalisations in < 1-year-olds during weeks 40, 2023, to 8, 2024, were compared to the number that would be expected after accounting for the background change in RSV circulation in the 2023/24 season, compared to 2022/23.

RESULTS

We estimated 9364-9875 RSV hospitalisations less than expected, corresponding to a 74%-75% reduction.

Clinical Differences between SARS-CoV-2 and RSV Infections in Infants: Findings from a Case-Control Study

Infants are a unique pediatric group due to their high hospitalization rates and unfavorable outcomes from acute infectious diseases. Understanding the clinical differences and aftereffects of SARS-CoV-2 in comparison to other prevalent viruses in this age group, like RSV, is crucial for effective management. We conducted a retrospective case-control study of infants hospitalized with SARS-CoV-2 or respiratory syncytial virus (RSV) infection in one year, in a tertiary pediatric hospital in Bucharest, Romania. A total of 188 infants were included in the analysis in a 1:1 ratio (94 with SARS-CoV-2 infection and 94 with RSV infection). Infants with COVID-19 were 10.2 times more likely to have fever (p < 0.001) and 2.4 times more likely to have diarrhea (p = 0.016). Conversely, infants with RSV were 2.5 times more likely to have a cough (p < 0.001), 3.0 times more likely to have nasal congestion (p < 0.001), and 14.7 times more likely to present with dyspnea (p < 0.001). Increased lymphocyte count was more common in infants with RSV (p = 0.008), while lymphopenia was more frequent in infants with SARS-CoV-2 (p = 0.011). The median length of hospital stay was one day longer in infants with RSV infection (5 days vs. 4 days). Overall, infants with RSV infection had a 27.3-fold increased risk of developing respiratory failure (p < 0.001), while infants with COVID-19 had a 5.8-fold increased risk of laryngitis (p = 0.003). Our findings suggest that infants with SARS-CoV-2 infection may present with polymorphic symptoms, mostly dominated by fever, whereas infants with RSV often present with respiratory symptoms. Laboratory differentiation between the two infections is challenging; therefore, the use of rapid antigen or molecular diagnostic tests is crucial for accurate diagnosis, epidemiologically appropriate measures, and effective management. Continued surveillance of both viruses in infants, and beyond, and the implementation of specific control measures are needed to mitigate their impact on this vulnerable pediatric group.