Fever, Cough & Stomach Ache: Differential Diagnosis (COVID, Flu, RSV & More)

Triad of fever + cough + abdominal pain suggests systemic viral illness. Key differentials:

Comparison Table

Illness	Fever	Cough	GI Symptoms	Distinguishing Features	Test
COVID-19	Common	Dry, persistent	Diarrhea, nausea, anorexia (20–30%)	Anosmia/ageusia, multisystem	Rapid Ag / PCR
Influenza (A/B)	High, abrupt	Dry, severe	Nausea, vomiting (more in kids)	Myalgia, headache, fatigue prominent	Rapid Ag / PCR
RSV	Low-grade	Wheezing, wet	Poor feeding, vomiting (infants)	Bronchiolitis <2 yrs; mild in adults	PCR / Ag
Adenovirus	Variable	Barking (croup) or dry	Diarrhea, vomiting common	Conjunctivitis, pharyngitis, hepatitis risk	PCR panel
Parainfluenza	Low-grade	Barking (croup)	Rare	Croup syndrome (stridor)	PCR panel
Enterovirus / Coxsackie	Common	Variable	Diarrhea, herpangina, HFMD	Summer/fall; rash, mouth ulcers	Clinical / PCR

Red Flags: Seek Care

• Dehydration (↓urine, dry mucosa, lethargy)
• Respiratory distress (retractions, grunting, SpO₂ <94%)
• Persistent fever >3 days (adult) / >24 hrs (infant <3 mo)
• Severe abdominal pain (appendicitis, intussusception)
• Immunocompromised, pregnant, elderly, chronic disease.

Initial Home Care

• Fluids, rest, antipyretics (acetaminophen/ibuprofen).
• Isolate per CDC (COVID/flu).
• Test for COVID/flu if high-risk or need antiviral (Paxlovid, Tamiflu ≤48 hrs).