12e - Rapid escalation of enterovirus D68 cases in northern Italy associated with respiratory infection, August-September 2024

Background : The emergence of enterovirus D68 (EVD68) as a notable respiratory pathogen with the potential to cause paralysis similar to poliomyelitis represents a significant public health concern. Nevertheless, no dedicated surveillance systems have been established in Europe to monitor EVD68. In response, a laboratory-based surveillance was conducted in Lombardy, Northern Italy, to assess the epidemiological and genomic features of enteroviruses.

Methods : The study encompassed both outpatients presenting with influenza-like illness (ILI), identified within the respiratory virus surveillance system, and inpatients with severe acute respiratory infection (SARI) across 13 hospitals. Samples positive for EV were tested by a real-time RT-PCR assay for the detection of EVD68. The VP1/VP3 gene was sequenced.

Results : A total of 506 respiratory EV-positive samples were collected between 1 January and 19 September 2024. Of these, 42.1% were from ILI outpatients and 57.9% from SARI inpatients. EVD68 was identified in 21.3% (n= 108) of EV-positive samples of which 79.6% in SARIs. The mean weekly EVD68 positivity rate was 4.4% (range: 0%–25%) up to 15 July 2024. Subsequently, a statistically significant increase was observed, reaching 49.4% (range: 5.6%-96.2%) as of 19 September 2024. From 19 August onwards, EVD68 constituted approximately 90% of EV cases. The median age of those testing positive for EVD68 was 39 years (interquartile range: 59 years), and 55.3% of these individuals were male. The preliminary sequence data indicate that the lineage is B3. Whole genome sequencing is ongoing.

Conclusions : The shift in the age profile, coupled with the high prevalence of EVD68, indicates that the outbreak predominantly affects adults. These findings emphasise the necessity for enhanced laboratory surveillance and rapid diagnostic capabilities for EVD68 to inform public health interventions.