Is Scarlet Fever Contagious?

  • Medical Author:
    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

Scarlet Fever Incubation Period

The incubation period for scarlet fever has a fairly wide range from about 12 hours to seven days. Individuals are contagious during this first subclinical or incubation period and during the acute illness. The primary strep infection is the contagious aspect.

What is scarlet fever?

Scarlet fever (also termed scarlatina) is an illness characterized by a bright red rash that can cover most of the body and is caused by a toxin secreted by group A streptococci, a type of gram-positive coccus-shaped (round) bacteria. Scarlet fever usually occurs in individuals that have had a strep throat infection or occasionally in those who have had streptococcal skin infection. The majority of people who get scarlet fever are between about 5-12 years of age. (It rarely occurs in babies under 2 years of age.)

Is scarlet fever contagious?

Scarlet fever may be contagious if a person becomes infected with a group A streptococcal bacterial strain that produces the scarlet fever toxin. However, not all people who get group A streptococcal infections develop scarlet fever; only a small percentage of these patients go on to develop scarlet fever.

How will I know if I have scarlet fever?

Individuals with scarlet fever usually have some or most of the following symptoms and signs:

The red rash may develop later than other symptoms (up to about seven days later). The physician can give a clinical diagnosis from the patient's history, physical exam, and possibly a rapid strep test; in some individuals, a throat culture may be done to determine if group A strep is the infecting bacteria.

How is scarlet fever transmitted?

The bacterial infection (strep throat or skin infection) that results in scarlet fever is contagious, but some people will get the infection (such as strep throat) without going on to develop scarlet fever. Consequently, scarlet fever spread is the secondary result of the way most group A streptococcal infections are spread -- by direct person-to-person contact (kissing, touching mucus membranes, for example) and by indirect methods such as contaminated eating utensils, cups, and other objects used by infected individuals. However, not all individuals who get group A streptococcal infections will develop scarlet fever.

Medically Reviewed by a Doctor on 11/7/2016

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