In measles (synonyms: Measles virus infection; Measels; Morbilli (measles); ICD-10-GM B05.-: Measles) is an infectious disease caused by the morbillivirus (measles virus; of the family Paramyxoviridae, genus Morbillivirus). Along with infectious diseases such as mumps or chickenpox, it is one of the typical childhood diseases. Humans currently represent the only relevant pathogen reservoir. Occurrence: The disease occurs worldwide. It is most common in developing countries. In Germany, the incidence continues to decrease due to recommended vaccination. The contagiousness of the pathogen is very high. Measles is one of the most contagious diseases of all.To quantify the contagiousness mathematically, the so-called contagiousness index (synonyms: contagiousness index; infection index) was introduced. It indicates the probability with which a non-immune person becomes infected after contact with a pathogen. The contagiousness index for measles virus is 0.95, which means that 95 out of 100 unvaccinated persons become infected after contact with a measles-infected person.Manifestation index: Approximately 95% of measles-infected persons become recognizably ill with measles. Seasonal incidence of the disease: Measles occurs more frequently from April to July. The pathogen is transmitted (infection route) via droplets that are produced when coughing and sneezing and are absorbed by the other person via the mucous membranes of the nose, mouth and possibly the eye (droplet infection) or aerogenically (through droplet nuclei containing the pathogen (aerosols) in the exhaled air) or through contact with infectious material such as secretions from the nose. The incubation period (time from infection to the onset of the disease) is 8-10 days to the onset of the catarrhal stage (inflammation of the mucous membranes) and 14 days to the onset of the exanthema (skin rash). The disease can be divided into four stages:
- Incubation period
- Prodromal phase – phase in which there is a nonspecific inflammation of the upper respiratory tract with fever, cough, rhinitis (nasal mucosa inflammation), conjunctivitis (conjunctivitis).
- Exanthem stage – phase in which the rash occurs.
- Convalescence (recovery)
Frequency peak: the disease occurs mainly in infancy and school age. With increasing age, it decreases again.In Germany, almost every second measles disease now occurs in adults. Approximately 30 million people worldwide contract measles each year. The incidence (frequency of new cases) is approximately 2 cases per 100,000 inhabitants per year. The achievement of measles elimination is equated by the World Health Organization (WHO) with an incidence of less than 0.1 diseases per 100,000 inhabitants per year. This goal has already been achieved in the USA and Finland. The duration of infectivity (contagiousness) is from 5 days before the onset of exanthema to 4 days after the onset of exanthema.The disease leaves lifelong immunity. Reinfection – especially after vaccination – is possible. Course and prognosis: Overall, the course depends on the general condition of the patient and on the therapy. For more information on the course of the disease, see above under the “Four phases of the disease”. Complications such as otitis media (inflammation of the middle ear) and pneumonia (lung inflammation) can occur during the course of the disease. These occur mainly in children under 5 years of age and in young adults over 20 years of age. What is feared is the development of post-infectious encephalitis (inflammation of the brain, due to a past infection), which occurs in approximately 0.1% of those who contract the disease. In addition, infection with morbillivirus leads to temporary immune insufficiency (immunodeficiency), which favors bacterial superinfection. The lethality (mortality related to the total number of people suffering from the disease) in post-infectious encephalitis is 10 to 20%. Vaccination: Vaccination against measles is available. Even in unvaccinated, otherwise healthy persons, the outbreak of the disease can still be prevented by timely vaccination after infection. In Germany, direct or indirect detection of the pathogen is reportable by name according to the Infection Protection Act (IfSG), insofar as the evidence indicates an acute infection.
