What could be causing my symptoms of diarrhea, stomach sickness, soreness, fever, and itchy red blotches from bug bites, which my relative has also developed after I did, following a recent trip?

Likely Diagnosis and Immediate Management

You and your relative most likely have acute viral gastroenteritis (norovirus), which is highly contagious and explains the sequential illness pattern, though tickborne illness must also be considered given the prominent bug bites and systemic symptoms. 1, 2

Primary Diagnostic Considerations

Most Probable: Acute Viral Gastroenteritis

• Norovirus characteristically presents with violent vomiting, nonbloody diarrhea, headache, body aches, and low-grade fever (present in ~40% during first 24 hours), typically lasting 2-3 days 1
• The person-to-person transmission pattern (you first, then your relative 1-2 days later) strongly supports a viral etiology 1
• The absence of bloody stools and high fever makes bacterial causes (Salmonella, Shigella, Campylobacter) less likely 1, 2

Alternative Consideration: Tickborne Rickettsial Disease

• The prominent itchy red blotches from bug bites, combined with fever and systemic symptoms (headache, body aches), raises concern for tickborne illness 3, 4
• Diarrhea occurs in tickborne infections including ehrlichiosis and Rocky Mountain spotted fever, though it's not the primary feature 4
• Critical point: Only 60-68% of patients with tickborne diseases recall the actual tick bite, so absence of remembered tick attachment should not exclude this diagnosis 3
• Both you and your relative having similar symptoms after shared outdoor exposure increases suspicion for vector-borne disease 3

Recommended Diagnostic Approach

Immediate Assessment Required

• If fever persists beyond 48 hours, exceeds 38.5°C, or if bloody stools develop, seek immediate medical evaluation 1, 2
• Signs requiring urgent care include: altered mental status, decreased urine output, severe abdominal pain, or inability to maintain hydration 1

Testing Indications

• No stool testing is needed if symptoms remain mild and self-limited 3, 1
• Pursue stool testing only if: diarrhea persists ≥14 days, high fever develops, bloody stools appear, or severe dehydration occurs 3, 1
• If fever persists beyond 72 hours or worsens, blood work including complete blood count should be obtained to evaluate for tickborne illness 3, 2

Management Strategy

Supportive Care (Primary Treatment)

• Oral rehydration therapy is the mainstay of treatment 1
• Resume normal diet as tolerated 1
• Antihistamines (oral) can reduce itching from bug bites 3
• Cold compresses may help local bite reactions 3

When Antibiotics Are NOT Indicated

• Do not pursue antibiotics for uncomplicated gastroenteritis without fever or bloody stools 3, 1
• The swelling and inflammation from insect bites is caused by mediator release, not infection—antibiotics are not indicated unless secondary infection develops 3

When to Consider Empiric Antibiotics

• If fever with diarrhea persists beyond 48-72 hours, empiric treatment with azithromycin 500 mg daily for 3 days should be considered 3, 2
• This covers both invasive bacterial gastroenteritis and potential tickborne pathogens 3, 2

Critical Red Flags

Seek Immediate Medical Attention If:

• Fever exceeds 38.5°C or persists beyond 48-72 hours 1, 2
• Bloody stools develop 1, 2
• Signs of severe dehydration (decreased urination, dizziness when standing, confusion) 1
• Severe or worsening headache with stiff neck 3
• Expanding rash or development of dark scab-like lesions at bite sites (suggests tickborne disease) 3

Common Pitfalls to Avoid

• Do not assume simple gastroenteritis when fever is prominent—this requires broader evaluation for invasive pathogens and tickborne diseases 2
• Do not dismiss the bug bites as incidental—the combination of systemic symptoms with prominent bite reactions warrants consideration of vector-borne illness 3, 4
• Do not use antibiotics for the bite reactions themselves unless clear signs of secondary bacterial infection develop 3
• Most insect bite reactions are IgE-mediated and self-limited, requiring only symptomatic treatment 3

Expected Clinical Course

• If viral gastroenteritis: symptoms should improve within 2-3 days 1
• If tickborne illness: symptoms typically worsen over 3-7 days without treatment 3
• If no improvement occurs within 72-96 hours, or if symptoms worsen, medical evaluation is mandatory 5, 2