Enteroviruses (EV) are found worldwide. In temperate regions such as France, an increase in enterovirus infections is observed every year during the summer and fall. A summer peak is usually seen in June and July, followed by a second, smaller peak in the fall. While most EV infections cause few or no symptoms, some infections can lead to severe complications, primarily meningitis, depending on age, the immune system (deficiency in humoral immunity), or the type of EV.

Toward a resurgence of significant enterovirus circulation this summer

The low circulation of enteroviruses (EV) observed in France since 2020, linked to COVID-19 containment measures, persisted through 2022, with EV infection levels well below the peaks observed between 2016 and 2019.

This has led to a larger pool of children who are more susceptible to EV infections, which may partly explain the increase in the proportion of neonatal infections observed in 2022 (25.7% of EV infections compared to 12.8% over the 2016–2021 period).
In 2023, while the number of EV infection cases reported to the Enterovirus Surveillance Network (RSE) remains, as of this report, well below the levels observed prior to 2020, a resurgence of EV infections as of July 5, 2023, appears to have begun in week S26 (June 26 to July 2).

The number of emergency department visits and hospitalizations for viral meningitis observed in the OSCOUR network has indeed been increasing since week S23 and has since reached levels comparable to those of 2018, which could indicate an expected summer peak in the coming weeks.

Vigilance is therefore still warranted throughout the summer of 2023 in light of any resurgence of EV infections and viral meningitis cases, particularly among very young children.

Alert Remains in Effect Regarding the Increase in Severe Neonatal Infections Associated with Echovirus 11

Santé publique France and the National Reference Center for Enteroviruses and Parechoviruses are maintaining their alert regarding the unusual increase in severe neonatal infections reported by the enterovirus surveillance network in connection with the circulation of a new variant of echovirus-11 detected since June 2022 and never previously identified.

Between July 2022 and March 2023, 9 newborns under 7 days old (including 4 sets of twins) were infected with this E11, of whom seven died (including 3 sets of twins). Following the alert, several cases of severe neonatal E11 infections with similar clinical presentations were reported in other European countries, and an additional case was reported in France in July.

The severe neonatal E11 infections reported in 2022–2023 are unusual and cause for concern. They can indeed worsen rapidly and suddenly, be associated with serious complications (liver or multi-organ failure), and lead to death in a large number of cases. The excess mortality observed in 2022–2023 could be explained by increased circulation of echovirus 11, but also by the characteristics of this new variant, which are currently under investigation. Other risk factors for mortality, such as acquiring the infection within the first 7 days of life, prematurity, and low birth weight, may also play a role.

The occurrence of a case in early July in the country confirms that echovirus 11 is still circulating and necessitates maintaining vigilance throughout the summer.

What are Santé publique France’s recommendations for healthcare professionals?

Given the current circulation of enteroviruses and a possible resurgence of enterovirus infections this summer, particularly among young children, Santé publique France and the National Reference Center for Enteroviruses and Parechoviruses are urging healthcare professionals to exercise particular vigilance in cases of severe clinical presentations, especially neurological ones, and in any severe neonatal infection where an EV infection must be considered and investigated.

They emphasize the importance of collecting appropriate specimens for EV genome testing (blood, nasopharyngeal swabs, stool) in all cases of severe clinical presentations. As such, any neonatal infection or severe neurological condition associated with an EV infection must be reported to the CNR, and specimens must be sent to complete virological investigations (including sequencing).