Differential Diagnosis
- Single most likely diagnosis
- Rhinovirus infection: This is the most likely diagnosis given the symptoms of headache, sore throat, nasal congestion, runny nose, and constant rhinorrhea. Rhinovirus infections are a common cause of the common cold, which presents with these exact symptoms. The presence of a friend and brother with similar symptoms also supports a highly contagious viral etiology like rhinovirus.
- Other Likely diagnoses
- Adenovirus infection: Adenovirus can cause similar symptoms to rhinovirus, including sore throat, runny nose, and fever. It's also highly contagious and can cause outbreaks, making it a plausible diagnosis given the epidemiological history.
- Influenza: Although the temperature is only slightly elevated at 37.7 C, which is not typically as high as seen in influenza, it's still a consideration, especially during flu season. The symptoms of headache, sore throat, and nasal congestion can be seen in influenza, but the lack of high fever and systemic symptoms like myalgias makes it less likely.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Influenza: Despite being less likely due to the mild temperature, influenza can be severe and even life-threatening, especially in certain populations. It's crucial not to miss this diagnosis, especially if the patient's condition worsens or if they belong to a high-risk group.
- Rare diagnoses
- Parainfluenza: This virus typically causes croup in young children, making it less likely in a 16-year-old. However, it can cause a range of respiratory illnesses, including mild upper respiratory symptoms.
- Respiratory syncytial infection (RSV): RSV primarily affects young children and infants, causing lower respiratory tract infections like bronchiolitis and pneumonia. It's rare for RSV to cause significant illness in healthy teenagers, making it an unlikely diagnosis in this case.