Diphtheria (synonyms: croup; diphtheria; croup; ICD-10-GM A36.-: diphtheria) is an infectious disease caused by the toxin of the gram-positive Corynebacterium diphtheriae (or other species, e.g., C. ulcerans).
Humans currently represent the only relevant pathogen reservoir for Corynebacterium diphtheriae, C. ulcerans, and C. pseudotuberculosis.
Occurrence: Infection occurs worldwide.
In order to quantify the contagiousness (infectiousness or transmissibility of the pathogen) mathematically, the so-called contagiousness index (synonyms: contagiousness index; infection index) was introduced. It indicates the probability of a non-immune person becoming infected after contact with a pathogen. The contagiousness index for diphtheria is 0.1-0.2, meaning that 10-20 out of 100 unvaccinated persons become infected after contact with a diphtheria-infected person.Manifestation index: Approximately 10-20% of diphtheria-infected persons become recognizably ill with diphtheria.
Seasonal accumulation of the disease: Diphtheria occurs more frequently in autumn and winter.
Transmission of the causative agent (route of infection) usually occurs via droplet infection in respiratory infestations. Contact and smear infection are also possible. In cutaneous diphtheria, toxin-producing pathogens are detected in wounds.
Human-to-human transmission: Yes, but extremely rare. It is usually animal (pets such as dogs and cats)-to-human transmission.
The incubation period (time from infection to onset of disease) is between 2 and 5 days, usually 4 days. Then a local infection develops first, depending on the entry site, among other things as throat, eye, skin diphtheria. Here, the toxin leads to necrosis (local tissue destruction), which adheres firmly to the mucosa (so-called pseudomembranes).
Frequency peak: The disease occurs predominantly in children of preschool age.
In industrialized countries, the disease is rather rare. In Russia, however, the prevalence (disease frequency) is increasing.
The duration of infectivity (contagiousness) lasts as long as the pathogen is detectable in secretions and wounds. In untreated persons, this corresponds to a period of two weeks (rarely more than four weeks). With antibiotic treatment, the infected persons are only infectious for 2-4 days.
Course and prognosis: The disease is systemic (affecting the entire organism) and usually affects the respiratory tract in the sense of tonsillitis (inflammation of the tonsils) and pharyngitis (inflammation of the throat). In this case, there is angina with adherent gray-white coatings on the pharyngeal mucosa (pseudomembranes); an attempt to detach these quickly leads to bleeding. The disease is often accompanied by fever. The earlier therapy is started, the better the prognosis. As a rule, contact persons are also treated in order to prevent the spread of the pathogen.
The lethality (mortality in relation to the total number of people infected with the disease) is about 5-10%.
Vaccination: Vaccination against diphtheria is available and is one of the recommended vaccinations. Infants from 3 months of age can be vaccinated. Vaccination largely prevents disease, but not infection or colonization. Consequently, germ carriers can also occur among the vaccinated.
In Germany, the disease is notifiable according to the Infection Protection Act (IfSG). The notification has to be made by name in case of suspected disease, illness as well as death.