Infectology

Passage of loose or watery stools, typically at least three times in 24 hours, due to increased water content of stool from impaired absorption or active secretion.

1. Acute: ≤14 days

2. Persistent: >14 but <30 days

3. Chronic: >30 days

Diarrhea with visible blood or mucus, often accompanied by fever and abdominal pain.

1. Viruses: Norovirus, Rotavirus, Adenovirus

2. Bacteria: Salmonella, Shigella, Campylobacter, E. coli, C. difficile

3. Protozoa: Giardia, Cryptosporidium, Entamoeba

1. Duration, frequency, and stool characteristics

2. Associated symptoms (e.g., fever, abdominal pain)

3. Evidence of dehydration (e.g., dark urine, decreased skin turgor)

4. Recent exposures (travel, food, occupational risks, pets)

Watery, large volume stools with cramping, bloating, and gas; rarely fever or occult blood.

Frequent, small volume, often bloody or mucoid stools with fever and abdominal pain.

1. Severe illness (fever ≥38.5°C, hypovolemia, >6 unformed stools/day)

2. Bloody diarrhea or mucous stools

3. High-risk patients (e.g., elderly, pregnant, immunocompromised)

4. Symptoms lasting >1 week

• Shiga toxin-producing E. coli (STEC)

• Entamoeba histolytica

Fluid repletion using oral rehydration solutions (ORS) containing water, salt, and sugar

1. Severe illness (high fever, hypovolemia, or severe abdominal pain)

2. Bloody diarrhea or signs of inflammation

3. High-risk patients (e.g., age ≥70, immunocompromised, pregnancy)

1. Azithromycin: Preferred for dysentery or fluoroquinolone-resistant pathogens.

2. Fluoroquinolones: Ciprofloxacin or Levofloxacin for 3–5 days.

For nonbloody diarrhea with absent or low-grade fever, but not in cases of dysentery unless paired with antibiotics.

1. Boiled starches (potatoes, rice, noodles) and crackers

2. Avoid high-fat and lactose-containing foods (except yogurt).

Higher risk of uncommon pathogens (e.g., CMV, parasites) and noninfectious etiologies.

Consumption of seafood or travel to cholera-endemic areas.

Giardia, Cryptosporidium, and Entamoeba.

Salmonella, Shigella, and Campylobacter.

higa toxin-producing E. coli (STEC).

Onset within 6 hours of food consumption.

Contact with infants in daycare centers or travel to mountainous regions.

Confirm with a culture for public health and susceptibility testing.

Computed tomography (CT).

In most cases of acute, nonbloody diarrhea, especially if not travel-associated.

Azithromycin or fluoroquinolones.

Clostridioides difficile infection.

Colonic wall thickening.

Giardia or Cryptosporidium.

Parasitic infections (e.g., Giardia, Cryptosporidium, Cyclospora) and noninfectious causes (e.g., inflammatory bowel disease).

Giardia, Cryptosporidium, and norovirus.

Development of unformed stools during or within 10 days of returning from travel to regions with poor sanitation and limited access to safe drinking water.

1. Visiting regions with poor sanitation.

2. Consuming food from street vendors.

3. Staying in all-inclusive resorts.

4. Traveling during warm and wet seasons.

• Southeast Asia (highest incidence).

• Latin America, Africa, and the Middle East (common for ETEC infections).

1. Enterotoxigenic Escherichia coli (ETEC)

2. Enteroaggregative E. coli

3. Campylobacter spp.

1. Norovirus (increasingly identified with molecular diagnostics).

2. Rotavirus.

1. Giardia lamblia

2. Cyclospora cayetanensis

3. Cryptosporidium parvum

1. Southeast Asia: Campylobacter spp.

2. Latin America, Africa, Middle East: Predominantly ETEC.

Development of antibiotic-associated diarrhea, particularly due to Clostridioides difficile.

Between 4 and 14 days after arrival, though it can occur sooner if bacterial concentration is high.

Malaise, anorexia, abdominal cramps, sudden watery diarrhea, occasional nausea/vomiting, and rarely colitis or fever.

ever, tenesmus, urgency, cramping, and bloody or mucoid diarrhea.

1. Giardia: Bloating, gas, nausea.

2. Cholera/Cryptosporidiosis: Profuse watery diarrhea.

3. Cyclospora: Watery diarrhea with intermittent symptoms.

1. Symptoms of colitis (bloody/mucoid stools, abdominal cramping).

2. Fever.

3. Predominantly upper GI symptoms (bloating, gas, nausea).

4. Persistent diarrhea (>10–14 days).

5. Recent antibiotic use (evaluate for C. difficile).

1. Stool culture (limited in identifying some E. coli strains).

2. Multiplex molecular testing (rapid but expensive and complex).

1. Cannot differentiate pathogenic from nonpathogenic E. coli.

2. Unable to identify viral agents or certain protozoa.

1. Shigella dysenteriae serotype 1 (Sd1)

2. Vibrio cholerae

1. S. dysenteriae (bloody diarrhea)

2. V. cholerae (watery diarrhea)

1. Enterotoxigenic E. coli (ETEC)

2. Norovirus

3. Campylobacter species

4. Vibrio cholerae

1. Shigella species (especially S. flexneri)

2. Campylobacter jejuni

3. Enteroinvasive E. coli

4. Entamoeba histolytica

1. Watery diarrhea with "rice-water" appearance

2. Vomiting and abdominal cramps without pain or tenesmus

3. Rarely associated with fever.

1. Bloody, mucoid stools

2. Abdominal cramps, fever, and anorexia

3. Tenesmus and small, frequent stools.

1. Hypovolemia and electrolyte imbalance (common in cholera)

2. Hemolytic-uremic syndrome (HUS)

3. Bacteremia

4. Reactive arthritis

1. Oral rehydration salts (ORS) for mild to moderate hypovolemia.

2. Intravenous fluids (e.g., Ringer's lactate) for severe hypovolemia.

1. Watery diarrhea: Only in severe cholera outbreaks.

2. Bloody diarrhea: Always treated empirically for Shigella.

1. Ciprofloxacin or azithromycin.

2. Metronidazole for amoebic dysentery if trophozoites are identified.

1. Severe dehydration.

2. Hypokalemia and metabolic acidosis.