An Epidemiological Study to Evaluate the RSV-Associated Lower Respiratory Track in Infections in Infants

Inclusion Criteria: * Written informed consent from parent/guardian to participate in this study * Male and female infants \<1 year of age (child must be entered before his/her 1st birthday) * Physician diagnosis of either a) acute LRI or b) apnea below: A) Acute LRI, defined as: 1. Medical diagnosis of bronchiolitis or pneumonia, or 2. In the absence of either of these diagnoses, LRI will be determined by the investigator after review of the medical record and must include at least one of the following: * Retractions * Wheezing * Rales or crackles * The presence of a new infiltrate, if a chest X-ray is available, which must be diagnosed by the ED physician or radiologist B) Apnea, defined as either: 1. Cessation of breathing for \>20 seconds by history or observation, or 2. Cessation of breathing for any length of time if accompanied by cyanosis or pallor, bradycardia as detected by a monitor, or 3. ED primary diagnosis of apnea * Parent/guardian has the ability and willingness to be available for a follow-up interview by telephone Exclusion Criteria: * Use of palivizumab or RSV-IGIV at any time prior to enrollment * Participation in trials of investigational RSV prophylaxis or therapeutic agents