It is a disease that one might think has disappeared, and yet: the year 2022 was distinguished by an unprecedented wave of imported cases of diphtheria, in France but also in several European countries.
Diphtheria due to the bacterium
Corynebacterium diphtheriae
is a highly contagious disease which is transmitted from man to man, through saliva, skin wounds and more rarely through objects soiled by the secretions of patients.
Main manifestation: angina which can be complicated by cardiac or neurological damage and lead to death.
There has been a vaccine against diphtheria for almost a century, and the French population is largely covered thanks to compulsory vaccination.
However, a handful of cases are recorded each year, imported by travelers or migrants.
But these usually remain very limited.
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However, in 2022 France alone recorded 30 cases, other countries even more: 118 in Germany, 69 in Austria, 52 in Switzerland, lists a communication unveiled at the European Congress of Clinical Microbiology and Infectious Diseases.
“
It is a fairly exceptional situation, however we cannot speak of a European epidemic, because there have been no transmissions to the general population:
these cases remain limited to people arriving from abroad, in a situation of vulnerability, often asylum seekers
”
, emphasizes Dr Sylvain Brisse, director of the national reference center for diphtheria and director of research at the Pasteur Institute, who conducted the genomic analysis of the strains of the bacterium.
Contamination linked to a lack of hygiene
The causes of this sudden wave (but now over in France) are not really known, but experts assume that the phenomenon is linked to poor vaccination coverage in the countries from which the patients originate (men in their twenties for the most part): primarily Afghanistan and Syria, destabilized by years of conflict.
“
The vaccine protects against the disease but not against the asymptomatic carriage of the bacterium
: it therefore continues to circulate.
And when the vaccination coverage of the population declines, we are witnessing the re-emergence of cases ,
”
explains Dr Brisse.
The forms of diphtheria observed were mainly cutaneous (therefore not very serious),
"
probably linked to a lack of hygiene and promiscuity
"
, continues the expert.
The patients were probably contaminated on the migratory routes or just before leaving.
The genomic study conducted by Dr Brisse revealed 4 different strains,
"
which suggests that there were 4 chains of transmission
".
It was also observed that some minority strains were resistant to macrolides.
“
It's a problem, because these antibiotics are used in patients allergic to amoxicillin or penicillin.
»
Let's never forget that germs know no borders.
Dr Sylvain Brisse, research director at the Institut Pasteur
“
The message to take away from all this is that these diseases, which we no longer know about here, can come back thanks to geopolitical imbalances, because they are not controlled in the countries of the South, recalls Sylvain Brisse
.
Let's never forget that germs know no borders
: it is therefore essential to maintain good vaccination coverage on our territory.
This is particularly effective in France because our recommendations provide for booster shots in adults at 25, 45 and 65 years old, then every 10
years, which is not the case in all countries.
»
In Austria, for example, a study carried out on 16,000 volunteers in 2021 and 2022 and presented at this same microbiology congress showed that a third of the population was insufficiently immunized against diphtheria.
The authors call for an intensification of the recall campaign among the oldest.
