Which infectious organism is most likely responsible for nasal congestion and fever in a previously healthy 18-month-old girl?

• A. Streptococcus pneumoniae
• B. Rhinovirus
• C. Influenza virus
• D. H. influenzae

Answer: (B)

The rhinovirus is a common cause of upper respiratory infections, especially in young children. This virus is known for causing symptoms such as nasal congestion and fever, which are typical presentations during viral upper respiratory tract infections. In previously healthy children, rhinovirus infections are often mild, resembling the common cold, but can still lead to noticeable symptoms like runny or congested nose and a low-grade fever.

While Streptococcus pneumoniae can lead to more severe infections, such as pneumonia or meningitis, it is less frequently the cause of mild upper respiratory symptoms like nasal congestion and fever. Influenza virus can also cause similar symptoms but typically presents with a more severe and abrupt onset, often accompanied by additional systemic symptoms like body aches and fatigue. Haemophilus influenzae, particularly type b, is associated with more severe diseases but is less common in cases presenting primarily with nasal congestion and fever in a previously healthy child. Thus, the rhinovirus best fits the described scenario, making it the most likely infectious agent responsible for these symptoms in this age group.