What could be the cause of symptoms including diarrhea, fatigue, nocturnal cough, vomiting, weakness, and body aches?

Acute Viral Gastroenteritis with Systemic Symptoms

This symptom constellation—diarrhea, fatigue, nocturnal cough, vomiting, weakness, and body aches—most likely represents an acute viral syndrome, with COVID-19 and acute gastroenteritis being the primary considerations that require immediate differentiation. 1, 2

Immediate Clinical Assessment

Obtain vital signs immediately, specifically looking for:

• Temperature elevation (fever occurs in 92.8% of COVID-19 cases and 96% of acute viral syndromes) 1, 2
• Oxygen saturation <92% (indicates severe disease requiring hospitalization) 1, 3
• Blood pressure for hypotension (systolic <90 mmHg requires urgent evaluation) 2
• Respiratory rate ≥30/min (indicates severe COVID-19) 1

Critical Diagnostic Considerations

COVID-19 as Primary Differential

COVID-19 testing should be obtained immediately, as gastrointestinal symptoms (diarrhea 6.1%, vomiting 52-55%, nausea) frequently occur and can precede respiratory symptoms by several days. 1, 3, 4 The combination of:

• Fever (present in 92.8% of cases) 1
• Cough (69.8% of cases) 1
• Fatigue (20.3-50% of cases) 1
• Gastrointestinal symptoms (diarrhea and vomiting occur in 48.9% when excluding anorexia) 4
• Body aches/myalgia (27.7% of cases) 1

This presentation strongly suggests COVID-19, particularly if there is recent exposure or community transmission. 1, 3

Importantly, diarrhea in COVID-19 patients is associated with lower mortality and may indicate a better prognosis, as the gastrointestinal tract may be more involved than the respiratory system in some patients. 4

Infectious Gastroenteritis

If COVID-19 testing is negative, acute infectious diarrhea becomes the leading diagnosis. 1, 5 The presence of:

• Fever (58-100% in bacterial causes like Salmonella) 1
• Vomiting/nausea (52-100% depending on pathogen) 1
• Body aches and fatigue (common in viral gastroenteritis) 5

Stool studies should be obtained only if the patient has: 1, 5

• Signs of severe dehydration
• Bloody stools (not mentioned in this case)
• Persistent fever beyond 3 days
• Immunocompromised status
• Recent hospitalization or antibiotic use (to exclude C. difficile)

The majority of acute diarrheal illnesses are self-limiting viral infections that do not require diagnostic workup. 5

Alternative Serious Diagnoses to Exclude

Tick-borne illness (Ehrlichiosis) must be considered if there is: 2

• Recent tick exposure or outdoor activities
• Travel to endemic areas
• The classic triad of fever (96%), headache (72%), and malaise (77%) 2

Obtain complete blood count looking for: 2

• Leukopenia
• Thrombocytopenia (<150,000/μL)
• Elevated hepatic transaminases

If tick-borne illness is suspected, start doxycycline immediately without waiting for laboratory confirmation, as delayed treatment can lead to severe disease or death. 2

Red Flags Requiring Immediate Hospitalization

Admit to hospital if any of the following are present: 1, 3, 2

• Oxygen saturation <92%
• Persistent hypotension (systolic BP <90 mmHg)
• Altered mental status or confusion
• Respiratory rate ≥30/min
• Evidence of organ dysfunction
• Severe dehydration unresponsive to oral rehydration

Management Strategy

If Mild-Moderate Symptoms Without Red Flags

Supportive care is the cornerstone of treatment: 1, 2, 5

• Oral rehydration with frequent small volumes of fluids 1, 5
• Early oral refeeding once vomiting subsides 1
• Antipyretics (acetaminophen or ibuprofen) for fever and body aches 2
• Rest until symptom resolution 2

Antiemetics can be used for symptomatic relief: 6, 7

• Ondansetron (serotonin antagonist) or metoclopramide (dopamine antagonist) for acute nausea/vomiting 7
• Use for the shortest duration necessary to control symptoms 7

Antidiarrheal medications (loperamide) can be considered if no fever or bloody stools are present. 1

Empirical Antibiotics

Do NOT start empirical antibiotics unless: 1, 5

• Bloody diarrhea is present
• Fever persists beyond 3 days
• Signs of invasive disease (severe abdominal pain, high fever, systemic toxicity)
• Immunocompromised status

If antibiotics are indicated, obtain stool culture BEFORE starting treatment, then use a fluoroquinolone (ciprofloxacin) or azithromycin for suspected bacterial gastroenteritis. 1

Common Pitfalls to Avoid

• Do not ignore the possibility of COVID-19 even with prominent gastrointestinal symptoms, as GI manifestations can dominate the clinical picture. 1, 4
• Do not order extensive stool studies in uncomplicated acute diarrhea without red flags, as most cases are self-limiting viral infections. 5
• Do not delay doxycycline if tick-borne illness is suspected based on epidemiological history, even without laboratory confirmation. 2
• Do not assume absence of respiratory symptoms excludes COVID-19, as GI symptoms can precede respiratory manifestations. 1, 4

Follow-Up

Re-evaluate if: 2, 5

• Symptoms persist beyond 5-7 days without improvement
• New symptoms develop (bloody stools, severe abdominal pain, altered mental status)
• Dehydration worsens despite oral rehydration attempts
• Fever persists beyond 3 days