Triple Viral Respiratory Co-Infection With Respiratory Syncytial Virus (RSV), Human Metapneumovirus (HMPV), and Influenza A (H1N1) Leading to Acute Respiratory Distress Syndrome (ARDS) in an Infant: A Case Report.

Viral respiratory infections are a major cause of morbidity in pediatrics. We report a rare case of triple infection with respiratory syncytial virus (RSV), human metapneumovirus (HMPV), and influenza A (H1N1) in a previously healthy nine-month-old infant, complicated by acute respiratory distress syndrome (ARDS). The patient presented with severe respiratory distress, elevated inflammatory markers, and bilateral alveolar infiltrates, requiring non-invasive ventilation. A point-of-care multiplex PCR using the BioFire® Respiratory Panel 2.1 plus (RP2.1plus; bioMérieux, Marcy-l'Étoile, France) detected all three viruses. Confirmatory testing with the Xpert® Xpress Flu/RSV quadriplex PCR (Cepheid, Sunnyvale, CA) showed low cycle threshold (Ct) values for RSV and H1N1. Despite antiviral treatment, the patient's condition worsened, requiring invasive mechanical ventilation for 60 days. This case highlights the rarity and diagnostic complexity of triple respiratory viral co-infection and underscores the role of multiplex PCR in rapid pathogen detection. The interpretation of Ct values may provide additional diagnostic information but should be considered within the clinical context.