Cases of diphtheria have emerged in two European countries. This can be spread by a sick or deathly carrier.
Transmission usually occurs through droplets of saliva or contact with the wounds of a sick person.
So far, eight cases have been recorded in Switzerland.
A further four have been identified on the island of Reunion, France.
Here, one adolescent and three adults over the age of 55 have tested for the illness.
These have not travelled abroad.
The Regional Health Agency of Reunion Island said it usually records an average of just two cases per year, according to RTBF.
These would typically have also travelled to a high-risk area, unlike in this year’s cases.
In Switzerland, eight people living in a centre for asylum seekers in Bern are understood to have been infected earlier this month.
READ MORE: Brexit LIVE: Remoaner bid to blame recession on EU exit shredded
He said: “We have a mortality that can go up to 10 to 20 percent in the absence of treatment.
“We have effectively forgotten about this disease because it has been virtually eradicated in Belgium thanks to vaccination, in fact.”
Diphtheria is an infection caused by bacteria strains called Corynebacterium diphtheriae.
It can lead to difficulty breathing, heart failure and paralysis.
In the worst instance, it can also cause death.
Additional reporting by Maria Ortega.