A 9-month-old child presents with fever, cough, dyspnea. The symptoms appeared 5 days ago after a contact with a person suffering from URTI. Objectively: the child is in grave condition. Temperature of 38°C, cyanosis of nasolabial triangle is present. Respiration rate - 54/min., nasal flaring during breathing. There was percussion dullness on the right below the scapula angle, and tympanic sound over the rest of lungs. Auscultation revealed bilateral fine moist crackles predominating on the right. What is the most likely diagnosis?