However, severe disease may develop in the following: Patients who are < 6 months old, older adults, or patients who are immunocompromised Patients who have underlying cardiopulmonary or neuromuscular disorders Diagnosis of RSV and hMPV Characteristic symptoms and signs, particularly during the usual season or a known outbreak Sometimes rapid antigen tests, reverse-transcription-polymerase chain reaction (RT-PCR), or viral culture (all done on nasal washings or swabs) RSV (and possibly hMPV) infection is suspected in infants and young children with bronchiolitis or pneumonia during RSV season.