In the United States, it has been estimated that RSV causes more than 90,000 pediatric hospitalization and 4500 deaths annually. Also, an association between severe RSV bronchiolitis in infancy and subsequent development of asthma or recurrent episodes of wheezing has been suggested.
How is RSV transmitted?
RSV transmission occurs by direct contact (inoculation) of infectious secretions into the eyes and nose. Infection can also occur through contact with large aerosol droplets or contaminated objects. Transmission can be prevented by frequent hand washing by parents and health care providers, avoiding exposure to people with respiratory infection, and avoiding crowded places with young children as much as possible during the RSV season.
Once a child is infected, RSV spreads to the lower respiratory tract (lower part of the lungs). There, RSV causes fluid retention in the lungs (pulmonary edema) and increased mucus secretions that can obstruct airflow.
How does the infection progress?
After the inoculation and an incubation period of two to eight days (time required for the infection to develop), RSV divides and spreads to the lower respiratory tract (lower anatomy of the lungs). There, RSV causes inflammation leading to cell death and sloughing of the lining of the small airways. This leads to fluid retention (pulmonary edema) and increased mucus secretion that leads to obstruction of the airflow. The result is the hallmark of bronchiolitis, hyperinflation, atelectasis, and wheezing (see "What are the symptoms and complications?"). Complete recovery usually requires four to eight weeks, during which patient has prolonged cough, wheezing, and changed lung function.
What are the symptoms and complications?
In most healthy children and adults, RSV infection resembles common cold. Symptoms usually begin with low-grade fever, rhinorrhea (runny nose) and some cough four to six days after exposure to virus. However, if a patient does not recover, the infection will lead to prolonged cough, wheezing (whistling sound during breath due to difficulty in breathing) and decreased lung function. Also, infants may be irritable, restless and nasal flaring and retractions may occur, indicating airway obstruction.
Complications include pneumonia and bronchiolitis. The hallmark symptoms of bronchiolitis are hyperinflation of the lungs, atelectasis (collapse of the airways), and wheezing. Furthermore, reactive airway disease and decreased pulmonary function has been identified in children who were previously infected with RSV. Severe respiratory infection in infants may cause increase susceptibility to long-term respiratory diseases, such as asthma, as child grows older.
How is RSV diagnosed?
Diagnosis of RSV infection can be made by virus isolation, detecting antigen or RNA of a virus, or a combination of these approaches. Despite the availability of multiple tests, most physicians rely on history of illness, physical examination, and x-ray to make the diagnosis because of the consistency in clinical signs and symptoms and high prevalence during the RSV season.
What treatments are available?
Treatment of upper respiratory RSV infection is primarily aimed at symptom alleviation similar to other viral infection that causes upper respiratory infections. No antibiotic therapy is offered without co-bacterial infection because antibiotics do not work in viral infections.
If an infection becomes severe and affects the lower respiratory, then this usually requires hospitalization. Patient may need, as required, respiratory therapy, hydration, administration of humidified oxygen and medications to help open the airways. In severe cases of hypoxia (low oxygen levels), intubation and ventilatory assistance will be required. In such cases, aerosolized ribavirin (Virazole®), an antiviral agent used for treatment of severe RSV infection, has demonstrated beneficial effect.
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