Scarlet fever is common. Children between the ages of five and twelve are particularly affected. In principle, however, people of any age can become infected. Find out more about the transmission routes and how long sick people are contagious.
Scarlet fever is an infectious disease. It is caused by the bacterium Streptococcus pyogenes. This pathogen occurs worldwide – and it is very contagious.
About 5 out of 1,000 children will get scarlet fever within a year. They are mainly infected in schools, kindergartens and day-care centers.
Contagion: How scarlet fever is transmitted
In most cases, scarlet fever is transmitted via the finest droplets of saliva containing bacteria, which are expelled when the infected person speaks, coughs or sneezes (droplet infection). If other people come into contact with these droplets – for example by inhaling them – they can become infected.
Transmission is also possible via contaminated objects (smear infection). The bacteria can stick to fittings, door handles or toys, for example.
After infection, it takes about one to three days for the first symptoms of scarlet fever to become noticeable. In the beginning, these are usually a sore throat and fever. The characteristic skin rash only becomes visible one to two days later, usually initially on the upper body.
Not every infection with Streptococcus pyogenes also leads to scarlet fever. Rather, the bacterium usually triggers other diseases. These include bacterial tonsillitis, erysipelas or bark lichen. Scarlet fever is only caused by certain strains of bacteria that are infected by so-called bacteriophages – certain viruses. The pathogens then form toxins, which trigger the characteristic skin changes in scarlet fever.
Scarlet fever: How long do sufferers remain contagious?
How long a person with scarlet fever is contagious depends largely on the treatment. The doctor usually prescribes an antibiotic. Then the person is usually no longer contagious 24 hours after starting to take it. Children who no longer have a fever and are feeling better can then go back to school, daycare or kindergarten.
The situation is different if antibiotics are not used. Sick people can then be contagious for a longer period of time – namely up to three weeks from the onset of the first symptoms.
Scarlet fever: Re-infection possible
Many childhood diseases – such as rubella – are characterized by the fact that you can only get sick once. Anyone who has been infected once has lifelong immunity to the respective pathogen.
Scarlet fever is different: it is possible to get infected again at a later date. This is because the bacteria release different toxins. In the future, anyone who becomes infected with scarlet fever will only be immune to the toxin produced by the causative bacterial strain – but not to other toxins.