Outbreak of Corynebacterium diphtheriae among asylum seekers in Belgium in 2022: operational challenges and lessons learnt.

Since 2022, European countries have been facing an outbreak of mainly cutaneous diphtheria caused by toxigenic Corynebacterium diphtheriae among asylum seekers. In Belgium, between 1 March and 31 December 2022, 25 cases of toxigenic C. diphtheriae infection were confirmed among asylum seekers, mostly among young males from Afghanistan. Multi-locus sequence typing showed that most isolates belonged to sequence types 574 or 377, similar to the majority of cases in other European countries. The investigation and management of the outbreak, with many asylum seekers without shelter, required adjustments to case finding, contact tracing and treatment procedures. A test-and-treat centre was organised by non-governmental organisations, the duration of the antimicrobial treatment was shortened to increase compliance, and isolation and contact tracing of cases was not possible. A vaccination centre was opened, and mobile vaccination campaigns were organised to vaccinate a maximum of asylum seekers. No more cases were detected between end December 2022 and May 2023. Unfortunately, though, three cases of respiratory diphtheria, including one death, were reported at the end of June 2023. To prevent future outbreaks, specific attention and sufficient resources should be allocated to this vulnerable population, in Belgium and at international level.