Diarrhea in Adults - Infectious

Definition

Infectious diarrhea in adults is the passage of three or more loose or watery stools per day due to bacterial, viral, or parasitic pathogens, often associated with abdominal cramps, fever, nausea, and dehydration.

Epidemiology

• Common worldwide, particularly in regions with poor sanitation and contaminated food or water
• Incidence higher in travelers to endemic areas (traveler’s diarrhea)
• Affects all age groups but may be severe in elderly and immunocompromised patients
• Bacterial causes more common in developing countries; viral causes (norovirus, rotavirus) in developed regions
• Seasonal outbreaks may occur for viral and bacterial pathogens

Etiology

• Bacterial: Escherichia coli (enterotoxigenic, enterohemorrhagic), Salmonella, Shigella, Campylobacter, Vibrio cholerae
• Viral: Norovirus, Rotavirus, Adenovirus, Astrovirus
• Parasitic: Giardia lamblia, Entamoeba histolytica, Cryptosporidium
• Transmission: fecal-oral route, contaminated water or food, person-to-person contact
• Risk factors: travel, immunosuppression, poor hygiene, consumption of undercooked or contaminated food

Pathophysiology

• Pathogens invade intestinal mucosa or produce enterotoxins causing secretory diarrhea
• Disruption of epithelial cells leads to malabsorption and osmotic diarrhea
• Inflammatory response triggers cytokine release, causing fever and systemic symptoms
• Fluid and electrolyte loss due to increased intestinal secretion and decreased absorption
• Severe infections may cause mucosal ulceration, blood in stools, and systemic toxicity