Viral Croup: The patient's symptoms of fever, vomiting, refusal to eat or drink, and stridor when crying are consistent with viral croup, a common illness in infants. The fact that stridor is absent when the patient is settled also supports this diagnosis.

Viral Gastroenteritis: The patient's symptoms of fever, vomiting, and refusal to eat or drink could also be consistent with viral gastroenteritis, which is a common cause of illness in infants.
Upper Respiratory Infection: The patient's symptoms of fever and stridor when crying could also be consistent with an upper respiratory infection, such as a cold or sinus infection.
Dehydration: The patient's refusal to eat or drink and vomiting could lead to dehydration, which is a common complication of illness in infants.

Epiglottitis: Although less common, epiglottitis is a life-threatening condition that can present with similar symptoms, including stridor and refusal to eat or drink. It is essential to consider this diagnosis to avoid missing a potentially deadly condition.
Bacterial Tracheitis: This is another life-threatening condition that can present with stridor and respiratory distress, and it is essential to consider this diagnosis to avoid missing a potentially deadly condition.
Foreign Body Aspiration: The patient's symptoms of stridor and refusal to eat or drink could also be consistent with foreign body aspiration, which is a medical emergency.

Anaphylaxis: Although rare, anaphylaxis can present with stridor and respiratory distress, and it is essential to consider this diagnosis in the differential.
Congenital Anomalies: Certain congenital anomalies, such as laryngomalacia or subglottic stenosis, can present with stridor and respiratory distress, although these are rare conditions.
Inborn Errors of Metabolism: Certain inborn errors of metabolism, such as mitochondrial disorders, can present with nonspecific symptoms, including fever and vomiting, although these are rare conditions.