Viral croup usually has a gradual onset and course. The symptoms often get worse at night. Initially, the child gets a cold with cough, coryza and low-grade fever. In about 12 to 24 hours, the cough becomes croupy (i.e. barky) with inspiratory stridor, causing varying degrees of respiratory distress with retractions and even cyanosis.
The duration of symptoms is usually 3-7 days. Examination reveals hoarse voice, coryza, a normal or minimally inflamed larynx and an increased respiratory rate with prolonged inspiratory phase and stridor.
Diagnosis is usually made on the basis of complete history and clinical examination. Usually, baseline investigations such as complete blood count are of no great significance as the results are non-specific.
Procedures: Laryngoscopy may be required in when any uderlying anatomic or congenital anomaly is suspected. Bronchoscopy is indicated in cases of recurrent croup when other respiratory disorders have to be ruled out .
Radiography: Plain X-ray films can help confirm the diagnosis of croup. The posterolateral and lateral neck films show funnel-shaped subglottic region with normal epiglottis. This is known as Steeple's sign and is present in 40 to 60% of the cases . It is also known as hour-glass or pencil point sign.
The treatment depends upon the severity of symptoms and degree of the respiratory distress. For mild disease, reassurance in addition to maintenance of oxygenation and fluid homeostasis is sufficient.
The prognosis of croup is excellent. Almost all of the cases of croup recover completely without any sequel of complications. Most of the patients can even get treated in the outpatient settings, whereas few of the cases might require hospitalization. Although the overall mortality rate in not exactly known, however a 10-year study shows the mortality rate to be less than 0.5% in intubated patients .
About 80% of the total cases of croup are caused by Parainfluenza viruses (type 1, 2 and 3), out of which about 66% of the cases are caused by types 1 and 2. Parainfluenza type 3 virus mostly causes bronchiolitis and pneumonia in young infants. Not much is known about parainfluenza type 4 virus. It may be the cause of minor childhood illness.
The remaining 20% of the cases of croup are caused by adenovirus, respiratory syncytial virus (RSV), enterovirus, coronavirus, rhinovirus, reovirus, influenza virus A and B and metapneumovirus  . Other rare causes of croup are measles virus, herpes simplex virus and varicella virus.
These viruses can spread through inhalation of infectious agents in the cough or sneeze of an infected person. They can also spread by contamination of hands with fomites or through touching of mucosa of eyes, mouth and/or nose.
Croup is primarily a disease of infants and younger children and is the most common cause of acute stridor in this age group. It is slightly more common in the male gender, the male-to-female ratio being 1.5:1.
It is common in children aged 7 months to 3 years. After 6 years of age, the occurrence of croup is very rare .
In North America, the peak incidence is in the second year of life affecting 5-6 cases per 100 children.
The common ports of entry of the virus are nose and nasopharynx. From there, the virus then spreads to the larynx and trachea resulting in inflammation and edema in these areas. The inflammatory infiltrate contains lymphocytes, histiocytes, plasma cells and neutrophils. An increased chloride secretion and decreased sodium absorption results in edema, thus narrowing the lumen of the air passages by accumulation of fibrinous exudates.
As croup is a contagious disease, contact with the affected individuals must be made as minimally as possible.
In febrile children, the presence of hoarseness, barking cough or acute inspiratory stridor is usually indicative of croup. Older children usually recover fully without any complications. In infants however, this might be a life-threatening condition.
Croup refers to infection of the airways that causes them to swell up. It is caused by a virus and usually affects male children under the age of 4 years. Symptoms are more common in winter months. The child develops flu-like symptoms with cough that sounds like a bark. Croup is usually not fatal and almost all children recover from it.