What Causes Scarlet Fever?

Scarlet fever is caused by group A streptococcus bacteria (or, more specifically, a toxin that the bacteria produce). These same bacteria can also cause several other illnesses, such as strep throat and toxic shock syndrome. Exposure to the toxin does not always cause scarlet fever -- some people are immune to it.

Scarlet Fever Disease

Scarlet Fever Causes

Scarlet fever is an illness caused by bacteria called group A streptococcus, the same bacteria that cause strep throat. Group A streptococcus (known as Streptococcus pyogenes) produces a toxin that causes scarlet fever symptoms. Some people are sensitive to this toxin; others have developed immunity. This is why two people in the same household can have a strep infection, but only one may develop scarlet fever.

Understanding Group A Streptococcus

Group A streptococcal (strep) infections are caused by group A streptococcus, a bacterium responsible for a variety of health problems. These infections can range from a mild skin infection or sore throat, to severe, life-threatening conditions. Some specific illnesses that group A streptococcus can cause include:

Strep throat
Scarlet fever
Impetigo (characterized by blisters that may itch)
Cellulitis (inflammation of connective tissue of the skin)
Erysipelas (hardened, painful skin lesions with raised borders)
Bacteremia (bloodstream infections)
Toxic shock syndrome (multiorgan infection)
Necrotizing fasciitis (flesh-eating disease).

Occasionally, group A streptococcus can also cause pneumonia.

Most people are familiar with strep throat, which along with minor skin infections, is the most common form of the disease. Health experts estimate that more than 10 million mild infections (throat and skin) like these occur every year.