Respiratory syncytial virus infection is a common cause of morbidity and death in pediatric patients. The clinical presentation ranges from mildly symptomatic to life-threatening pneumonia presenting as apnea and respiratory distress. Early suspicion must be mounted whenever respiratory symptoms are seen in young children, and various microbiological methods, most importantly polymerase chain reaction (PCR) that quickly identify viral genetic material, are used to confirm the diagnosis.
Responsible for more than 100,000 pediatric hospitalizations in the United States every year, respiratory syncytial virus (RSV) is considered to be the major cause of respiratory infections in infants and young children  . In fact, it is estimated that virtually all children up to age 3 will become infected with RSV, almost universally in a symptomatic fashion . However, several reports have emphasized its role as a respiratory pathogen across all age groups, including adults and the elderly, and approximately 11,000-17,000 deaths in the United States are attributed to RSV every year  . In milder cases, the clinical presentation is comprised of a cough, wheezing, fever, croup, and nasal congestion, with bronchiolitis being the most common type of infection  . In some patients, otitis media may be the initial manifestation of RSV infection . More severe forms, however, such as pneumonia, have been encountered more commonly in patients who exhibit any of the following risk factors: immunosuppression (B or T-cell inherited immunodeficiencies, human immunodeficiency virus infection, immunosuppressive therapy after marrow transplantation), premature birth, cyanotic congenital heart disease, chronic obstructive pulmonary disease (COPD), and older age    . Severe pneumonia can be life-threatening, both in infants and in adults, suggesting that an early diagnosis is pivotal.
Having in mind the rather common occurrence of RSV infection in clinical practice, particularly in young children, the physician must include this viral pathogen in the differential diagnosis of respiratory infections. The first step during workup is a thorough patient (or parent) interview that will assess the presence and course of symptoms, as well as the existence of any of the mentioned risk factors that could predispose to a more severe form of infection. The physical examination, particularly lung auscultation, is equally important, after which laboratory studies should be conducted. Microbiological testing is the cornerstone for the diagnosis of RSV infection, as the clinical presentation is nonspecific , and several methods have been described in the literature. Initially, viral cell cultivation was considered as the optimal procedure for isolation of RSV but the introduction of more rapid and also more reliable tests has removed it from regular use   . Direct antigen detection through immunofluorescent or enzyme immunoassays (IFA and EIA) has shown to be an efficient test to recognize RSV, but even better results are obtained through molecular studies that evaluate the presence of viral genetic material, such as polymerase chain reaction (PCR) and reverse-transcriptase PCR (RT-PCR)   . Unfortunately, their cost still is a major limiting factor .