Is Croup 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: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

What is croup?

Croup is infectious inflammation of the larynx and trachea usually in children. Croup typically interferes with breathing and causes a barking cough. The individual may be without a fever or have a low-grade fever. Viruses usually cause the inflammation of the larynx (voice box and vocal cords), trachea (windpipe), and/or bronchi that is characteristic of croup. Common viruses involved include adenovirus and respiratory syncytial virus, or RSV. Croup occurs mainly in children 6 months to 3 years of age, although older children and adults can be infected. Another type of croup is spasmodic croup. Spasmodic croup is almost identical to croup, but it is caused by an allergic reaction. Spasmodic croup occurs far less frequently than "croup" and has the same features, except it is not contagious.

Is croup contagious?

Croup is very contagious. It is spread by airborne droplets usually from an infected child to another child or adult. Croup viruses can be transferred to pregnant women, but the viruses that cause croup should not affect the fetus. However, pregnant women may have more serious symptoms with croup than non-pregnant women.

What is the incubation period for croup?

The incubation period for croup is relatively short. After exposure to the virus, symptoms of croup usually develop two to three days that may extend to seven days after exposure to viruses that cause the disease.

How long is croup contagious?

Croup may be contagious during the incubation period and for about seven to 10 days after symptoms develop.

How will someone know if he or she is infected with croup?

Croup causes a cough that sounds like a bark of a seal or a dog. Children with croup often have some trouble breathing because the airway is narrowed in this disease and breathing produces a sound (stridor) as air passes back and forth. Fortunately, many children (and adults) who get croup have very mild symptoms, and the disease resembles more of a bad cold with congestion. Croup is usually diagnosed simply by the doctor listening for the barking cough and stridor. However, sometimes other conditions can lead to similar symptoms, and occasionally a physician will order an X-ray of the child's neck to determine airway narrowing.

How is croup transmitted?

Croup is a very common ailment in children (average age is about 2 years old) and is considered to be highly contagious to other children. The viruses that cause group are easily spread through the air by mucus droplets during sneezing or coughing, through direct person-to-person contact, as well as by indirect contact when items such as toys, utensils, cups, and other objects have contaminated mucus on them from an infected child.

Croup Prevention

The infectious virus is most commonly transmitted by coughing or sneezing. Touching objects contaminated with infectious viral particles also allows transmission of the virus. Airborne viral particles can be infectious for about one hour.

How long does croup last?

Care of a child with croup involves decreasing the child's symptoms. Croup symptoms usually last for about three to seven days with the most severe symptoms at days two and three. Gradually, the symptoms abate and the child is usually cured of the disease in about a week; some patients exhibit symptoms for two weeks. Treatment of croup involves corticosteroids and nebulized epinephrine; antibiotics are not usually prescribed because croup infection is viral.

When should someone seek medical care for croup?

Although many individuals with croup can be effectively cared for at home, the following list of symptoms suggest that a child should be seen emergently if these symptoms develop:

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Medically Reviewed on 11/9/2017

American Academy of Pediatrics. "Croup and Your Young Child." May 5, 2015. <>.