Symptoms And Signs

The incubation period is 2-4 days. After signs of rhinitis and pharyngitis for a few days, the patient may become hoarse and have inspiratory stridor. There may be a mild to moderate fever. Involvement of the lower respiratory tract (bronchitis and bronchopneumonia) is seen in 30% of primary infections with type 3 virus. Severe croup is seen in 2-3% of primary infections with virus types 1 and 2. The parainfluenzaviruses are second only to respiratory syncytial virus as the cause of serious respiratory tract infections in infants and children. Parainfluenzavirus 1 and 2 most often give infections affecting the larynx and the upper trachea which may result in croup, while type 3 has a predilection for the lower respiratory tract giving bronchitis, bronchiolitis and bronchopneu-monia. Type 4 virus is less virulent, being associated with mild upper respiratory tract illness in children and adults. Due to the presence of protective maternal antibodies, serious illness due to parainfluenzavirus 1 and 2 infections is not seen before the age of 4 months. For type 3 virus serious illness is seen in the first months of life in spite of the presence of maternal neutralizing antibodies. The incidence of severe infections increases rapidly after the age of 4 months, peaking between the age of 3 and 5 years. The incidence is lower when the child reaches school age, and clinical disease from parainfluenzavirus 1, 2 and 3 infections is unusual in adult life. Reinfections with the same type of virus occur frequently, but with milder clinical manifestations. Differential diagnosis. Croup is occasionally caused by RSV and influenza-viruses. In bronchitis, bronchiolitis and bronchopneumonia in infancy other viruses, notably RSV, must be considered. Chlamydia trachomatis causes lower respiratory tract infections in early infancy, while Chlamydia pneumoniae and Mycoplasma pneumoniae are more commonly found in older children and young adults. The most important differential diagnosis to viral croup is bacterial croup or epiglottitis caused by Haemophilus influenzae type B. This is a life-threatening condition which usually starts without prodromal rhinitis and hoarseness. The patient has dysphagia and a higher fever than in viral croup and a toxic appearance. The epiglottis appears enlarged and inflamed on inspection. Respiratory distress does not tend to be diminished by bringing the patient into an upright position. Diphtheritic croup is now a rare illness in many countries. The condition is characterized by marked swelling of tonsils, the presence of membranes, prostration and high fever.

Dealing With Bronchitis

Dealing With Bronchitis

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