The primary objective of this study is to describe the incidence of RSV-associated LRI among infants <1 year of age presenting to the ED during selected shoulder months.

• The primary objective of this study is to describe the incidence of RSV-associated LRI or apnea (% RSV positive) among infants <1 year of age presenting to the ED during selected shoulder months. The total number of events will also be described.
• To characterize the clinical outcomes and demographic data of infants presenting to the ED with RSV-associated LRI or apnea
• To characterize the social burden (in the form of number of days lost from work by parent/ guardian) for these infants through 14 days after the index ED visit and through hospital discharge will also be described.
• Based on a sample of cases collected in a cohort of patients enrolled at or near the peak of RSV disease during the traditional season, a comparison of the rate of RSV between shoulder and peak periods will be described.
• To describe the overall rates of RSV-associated LRI or apnea based on the general ED statistics collected during the entire study period.

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

Eligible subjects with RSV results.