Viral Bronchiolitis: This is the most common cause of wheezing and fever in infants, typically caused by Respiratory Syncytial Virus (RSV). The age of the patient and the presentation of fever and wheeze are classic for this diagnosis.

Asthma: Although less common in this age group, asthma can present with wheezing and fever, especially if there's a history of atopy or previous episodes of wheezing.
Viral Pneumonia: Other viral pathogens can cause pneumonia, which may present with fever and wheezing, especially if there's an associated bronchospastic component.
Croup: This condition, often caused by parainfluenza virus, can present with a barking cough, stridor, and sometimes wheezing, along with fever.

Pneumococcal Pneumonia: Bacterial pneumonia, such as that caused by Streptococcus pneumoniae, can present with fever and wheezing and requires prompt antibiotic treatment.
Foreign Body Aspiration: This is a medical emergency that can cause sudden onset of wheezing and respiratory distress, often without fever. It's crucial to consider this diagnosis, especially if the onset is acute.
Congenital Heart Disease: Certain congenital heart defects can present with recurrent respiratory infections or wheezing due to increased pulmonary blood flow or congestion.

Cystic Fibrosis: Although rare, cystic fibrosis can present with recurrent respiratory infections and wheezing in infancy.
Immunodeficiency: Primary immunodeficiencies can increase the susceptibility to severe or recurrent infections, which might present with fever and wheezing.
Anaphylaxis: A severe, life-threatening allergic reaction that can cause wheezing, among other symptoms, though typically it would be associated with other signs such as rash, swelling, and hypotension.