Croup Health Article

Definition

Croup is one of the most common respiratory illnesses in children. It is an inflammation of the larynx and the trachea. When a child has croup, that portion of the airway just below the vocal cords narrows and becomes swollen, making breathing both noisy and labored.

Description

Croup is a broad term describing a group of illnesses that affect the larynx, trachea, and bronchi. The key symptom is a harsh, barking cough. One of the most common respiratory illnesses in children, croup is frequently noted in infants and children and can have a variety of causes. Before the days of antibiotics and immunizations, croup was a dreaded and often deadly disease usually caused by the diphtheria bacteria. Though in the early 2000s cases of croup are normally mild, it can still be dangerous. Croup affects the vocal cords and the area just below, the voice box, or larynx, and the windpipe, or trachea. The lower breathing passages (bronchi) may also be affected. Swelling of these areas causes the airway to narrow, which makes breathing difficult. It is also sometimes called laryngotracheitis, a medical term describing the inflammation of the trachea and larynx.

The characteristic symptoms of croup can be better understood by knowing the anatomic makeup of a child's larynx. Small children typically have quite a narrow larynx, so even a slight decrease in the airway's radius may lead to a large decrease in the air flow, leading to the symptoms of croup.

There are two primary types of croup: viral and spasmodic. Viral croup is caused by a viral infection in the trachea and larynx. It often starts with a cold that over time develops into a barking cough. When the child's airway becomes increasingly swollen and more mucus is secreted, it becomes more challenging to breathe. Breathing gets increasingly noisy, and a condition known as stridor may occur. (Stridor is a sign of respiratory obstruction that presents as a high-pitched, coarse, musical sound that occurs during breathing.) Children with viral croup usually have a low-grade temperature, but a few may have fevers up to 104°F (40°C). As breathing requires more effort, the child may stop eating and drinking. The child may also become too fatigued to even cough. If the airway continues to swell, it may approach a point at which the child can no longer breathe. Stridor is fairly common with a mild case of croup, especially if the child is active or crying. However, if a child has stridor at rest, the child may have severe croup. Symptoms are usually worse at night. The symptoms peak between 24 and 48 hours and usually resolve within one week.

Spasmodic croup is usually precipitated by an allergy or mild upper respiratory infection. It can be quite alarming, both because of the noise of the cough and because it usually comes on suddenly in the middle of the night. A child may go to sleep with a mild cold and wake up a few hours later, gasping for air. In addition, the child may have a cough that sounds like a seal barking, and will have a hoarse voice. Children with spasmodic croup normally do not have a fever.

Spasmodic croup can sometimes be difficult to differentiate from viral croup. Although spasmodic croup is associated with the same viruses that cause viral croup, spasmodic croup tends to recur and may be an indication of some type of allergic reaction instead of a direct infection.

Transmission

The viruses causing croup are highly contagious and easily transmitted between individuals through sneezing and coughing. It is usually transmitted via the respiratory route, entering through the nose and nasopharynx.

Demographics

Croup accounts for about 15 percent of all respiratory tract infections in children seen by physicians. It typically is seen in late fall and winter, and primarily occurs in children aged six months to three years. It has an annual peak incidence of 50 new cases per 1,000 children during the second year of life. Males are twice as likely as females to get the disease. The incidence decreases significantly after age six.