In recent years, Europe has faced its most significant outbreak of diphtheria in over seventy years, affecting vulnerable populations such as migrants and individuals experiencing homelessness. This alarming trend was highlighted by the Institut Pasteur and Santé publique France on June 4, 2025, urging increased vigilance and targeted actions to combat the spread of this serious disease.
Diphtheria is a highly contagious bacterial infection that primarily affects the respiratory system and can be fatal in severe cases. A significant spike in infections caused by the bacterium responsible for diphtheria, *Corynebacterium diphtheriae *, was observed in 2022 across several European countries, particularly among recent migrants. Research conducted by epidemiologists from Pasteur Institute and Santé publique France revealed that 362 cases were reported that year, as documented in a study published in *The New England Journal of Medicine*.
Rapid response measures, such as contact tracing and secondary case testing, have somewhat mitigated the outbreak’s impact, yet rare cases of infection continue to be reported among migrants and other at-risk populations. Since 2022, a total of 536 cases have been documented across Europe, with at least three resulting in fatalities.
A Low-Key Circulation
An analysis of samples from 362 infected individuals across ten different countries indicated that a staggering 98% were men, with a median age of 18. Most of these cases involved people who had recently emigrated. Among the infections, 77% were cutaneous, while 15% affected the respiratory system.
Notably, the outbreak primarily affected migrant populations from Afghanistan and Syria. This suggests that the infections did not result from contamination in these countries of origin, but rather during their migratory journeys or while housed in temporary accommodation in Europe. A statement from the institutes involved summarised the situation.
Genetic analyses of bacterial strains found that closely related strains were identified among individuals from various countries. Based on this, scientists hypothesize that there might have been a recent contact point outside the countries of origin that facilitated the contamination.
Despite the clarity around various aspects of this outbreak, uncertainties remain concerning geographic locations and conditions conducive to these infections. A genetic link has been established between the strain circulating in 2022 and a subsequent epidemic observed in Germany in 2025 , indicating that the bacterium continues to circulate quietly in Western Europe .
While experts note the effectiveness of vaccination programs for the general population, they emphasize the need for increased vigilance and proactive measures. This includes raising awareness among medical professionals and individuals in contact with these affected populations about the symptoms, encouraging vaccinations, and implementing appropriate antibiotic treatments.
The risks associated with diphtheria extend beyond just the migrant groups. Unvaccinated individuals, those who inject drugs, and older adults with pre-existing health conditions are also at risk. Experts like Isabelle Parent du Châtelet from Institut Pasteur and Santé publique France have highlighted these concerns.
The ongoing situation regarding diphtheria in Europe serves as a glaring reminder of the importance of continued public awareness and health interventions aimed at preventing further outbreaks. As communities grapple with the reality of this evolving health crisis, concerted efforts must be directed towards safeguarding vulnerable populations and ensuring that public health infrastructures are prepared for potential future challenges.
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