The patient's clinical presentation is characteristic of acute viral rhinosinusitis, commonly known as the common cold. The key indicators are the short duration of symptoms (6 days), the nature of the discharge (thin, clear rhinorrhea), the absence of high fever, and the fact that the symptoms are improving. Acute bacterial rhinosinusitis is generally suspected only when symptoms persist for 10 days or more without any improvement, are severe at onset (e.g., fever ≥39°C, purulent discharge), or worsen after a period of initial improvement ("double sickening"). Since this patient's condition is mild and resolving, a viral etiology is the most probable cause.

A. Streptococcus pneumoniae is a leading cause of bacterial sinusitis, which is inconsistent with the patient's improving, non-severe symptoms.

C. Moraxella catarrhalis is a common bacterial pathogen in sinusitis, but the clinical picture does not support a bacterial infection.

D. Haemophilus influenzae is a frequent cause of bacterial sinusitis; however, the patient's presentation points to a viral, self-limiting illness.

E. Staphylococcus aureus is a less common cause of community-acquired bacterial sinusitis and is not suggested by these mild, resolving symptoms.

1. Chow

A. W.

Benninger

M. S.

Brook

I.

et al. (2012). IDSA Clinical Practice Guideline for Acute Bacterial Rhinosinusitis in Children and Adults. Clinical Infectious Diseases

54(8)

e72–e112. (See Table 2

page e76

which outlines criteria for distinguishing viral from bacterial rhinosinusitis. Viral rhinosinusitis is characterized by a duration of less than 10 days with symptoms that are not worsening). https://doi.org/10.1093/cid/cis370

2. Rosenfeld

R. M.

Piccirillo

J. F.

Chandrasekhar

S. S.

et al. (2015). Clinical Practice Guideline (Update): Adult Sinusitis. Otolaryngology–Head and Neck Surgery

152(2suppl)

S1–S39. (See Section 2

"Distinguishing Viral vs. Bacterial Sinusitis

" which states that viral rhinosinusitis is far more common and typically resolves or improves within 10 days). https://doi.org/10.1177/0194599815572097

3. DiPiro

J. T.

Yee

G. C.

Posey

L. M.

Haines

S. T.

Nolin

T. D.

& Ellingrod

V. (2020). Pharmacotherapy: A Pathophysiologic Approach (11th ed.). McGraw-Hill. In Chapter 88

"Upper Respiratory Tract Infections

" the text clarifies that the vast majority of acute rhinosinusitis cases are caused by viruses and are self-limiting

with symptoms peaking at 3-6 days and resolving by day 10.