What are the differential diagnoses for an adult patient presenting with sore throat, chills, fever and diarrhea?

Differential Diagnoses for Adult with Sore Throat, Chills, Fever, and Diarrhea

The combination of sore throat with systemic symptoms (fever, chills) plus gastrointestinal involvement (diarrhea) suggests either a viral upper respiratory infection with concurrent gastroenteritis, or less commonly, a bacterial pharyngitis with systemic manifestations—prioritize Group A Streptococcal pharyngitis, viral pharyngitis (including influenza, COVID-19, EBV), acute infectious gastroenteritis, and consider atypical pathogens like Mycoplasma pneumoniae or Chlamydia pneumoniae.

Primary Infectious Differentials

Bacterial Pharyngitis with Systemic Features

• Group A β-hemolytic Streptococcus (GAS) is the most important bacterial pathogen in sore throat 1

  • Typically presents with fever and pharyngeal symptoms
  • Diarrhea is NOT a classic feature of streptococcal pharyngitis, making this less likely when prominent GI symptoms exist
  • Use Centor criteria (tonsillar exudates, tender anterior cervical lymphadenopathy, fever, absence of cough) to assess likelihood 1
  • If 3-4 Centor criteria present, consider rapid antigen testing 1

• Groups C and G β-hemolytic Streptococci can cause similar presentations to GAS 1

  • May present with exudative tonsillitis and cervical adenopathy
  • Clinical picture often indistinguishable from GAS pharyngitis

Viral Pathogens (Most Likely Given Constellation)

• Viral pharyngitis with concurrent gastroenteritis represents the most probable diagnosis given the symptom cluster
  • Most sore throats are viral and occur as part of common cold 1
  • Influenza can present with sore throat, fever, chills, and gastrointestinal symptoms 2
  • COVID-19 should be considered, as it can manifest with sore throat, fever, chills, and diarrhea 2
  • Epstein-Barr virus (infectious mononucleosis) causes pharyngitis with systemic symptoms, though diarrhea is less common 3

Atypical Bacterial Pathogens

• Mycoplasma pneumoniae and Chlamydia pneumoniae have been suggested as pharyngeal pathogens 1
  • Can cause pharyngitis with systemic symptoms
  • May present with fever and constitutional symptoms

Gastrointestinal-Predominant Differentials

Acute Infectious Gastroenteritis with Pharyngeal Involvement

• Norovirus is the leading cause of acute gastroenteritis in adults (58% of foodborne gastroenteritis cases) 4

  • Can present with fever, chills, and may have concurrent upper respiratory symptoms
  • Acute watery diarrhea lasting <7 days is typical 4

• Salmonella enterica accounts for 11% of gastroenteritis illness but 35% of hospitalizations 4

  • Presents with fever, diarrhea, and systemic symptoms
  • Sore throat would be coincidental or part of systemic inflammatory response

• Campylobacter jejuni causes gastroenteritis with fever and diarrhea 3

  • Notably associated with subsequent Guillain-Barré syndrome
  • Patients with diarrhea and abdominal pain show strong association with C. jejuni serology 3

Less Common but Important Considerations

Systemic Inflammatory Conditions

• Adult-onset Still's Disease (AOSD) can present with quotidian fever, sore throat, and bloody diarrhea (if concurrent ulcerative colitis) 5
  • Look for rash, arthralgia, marked ferritin elevation, neutrophilia
  • This is rare but important not to miss given potential for severe complications

Other Viral Syndromes

• Cytomegalovirus (CMV) can cause pharyngitis with systemic symptoms 3
• Adenovirus causes pharyngoconjunctival fever and may have GI symptoms

Clinical Approach Algorithm

1. Apply Centor criteria to assess streptococcal likelihood 1:

   • 0-2 criteria: Viral etiology most likely, no need for RAT or antibiotics
   • 3-4 criteria: Consider RAT for GAS; if positive, treat appropriately

2. Assess diarrhea characteristics 4:

   • Watery diarrhea + URI symptoms → viral gastroenteritis with concurrent pharyngitis
   • Bloody diarrhea → consider inflammatory bowel disease, AOSD, or invasive bacterial pathogens
   • Duration <7 days → acute gastroenteritis
   • Duration ≥14 days → persistent diarrhea requiring different workup

3. Consider epidemiologic factors:

   • Recent food exposure, sick contacts, travel history
   • Seasonal patterns (influenza in winter months)
   • COVID-19 exposure or community prevalence

4. Red flags requiring broader workup:

   • Severe systemic symptoms, immunosuppression, bloody diarrhea
   • Marked laboratory abnormalities (severe neutrophilia, thrombocytopenia, elevated ferritin) 5
   • Symptoms persisting >14 days

Key Pitfalls to Avoid

• Do not assume all sore throats with fever are streptococcal—most are viral 1
• Do not overlook the significance of diarrhea—this is NOT typical for streptococcal pharyngitis and suggests either viral syndrome or separate GI pathogen
• Do not routinely use antibiotics for low Centor scores (0-2 criteria) even with systemic symptoms 1
• Do not forget to consider COVID-19 and influenza, especially during appropriate seasons or with known exposures 2
• Biomarkers like CRP are not routinely necessary for acute sore throat assessment 1

The most parsimonious explanation for this presentation is concurrent viral upper respiratory infection and viral gastroenteritis, though bacterial pharyngitis (particularly GAS if Centor score is high) and specific viral syndromes like influenza or COVID-19 warrant consideration based on clinical scoring and epidemiologic context.