The largest diphtheria outbreak in Europe in seven decades, recorded in 2022, has been genetically linked to known migration routes across the continent rather than to patients’ countries of origin, according to a new study published in the New England Journal of Medicine. Researchers also found that the outbreak strain is connected to a 2025 epidemic in Germany, raising concerns about ongoing undetected transmission of Corynebacterium diphtheriae in Western Europe.
From January to November 2022, 362 cases were confirmed across ten countries. Most of the affected were male migrants aged 16 to 20, with Germany (118 cases) and Austria (66) reporting the highest numbers. Nearly all patients (96.1%) had either recently migrated, were in contact with migrant communities, or had newly entered the reporting country.
“Closely related diphtheria clones were detected in multiple European countries,” said Andreas Hoefer, PhD. “Our analysis illustrates that people who left their home countries without the disease contracted diphtheria on their way to the destination country where they were diagnosed.”
In April 2025, German authorities reported a new outbreak originally detected in 2022. The cases involved individuals experiencing homelessness, an elderly person, and an unvaccinated child.
