Infectious Gastroenteritis

Infectious gastroenteritis, commonly known as stomach flu or gastro, is an inflammation of the stomach and intestines caused by viruses, bacteria, or parasites. It's one of the most common illnesses worldwide, characterized by diarrhea, vomiting, and abdominal discomfort.

Overview

Infectious gastroenteritis is an acute inflammation of the gastrointestinal tract caused by various pathogens. Despite being commonly called "stomach flu," it's not related to influenza. This condition affects millions of people annually and is a leading cause of morbidity and mortality worldwide, particularly in developing countries and among young children and elderly populations.

The condition results from infection with viruses, bacteria, or parasites that irritate and inflame the stomach and intestinal lining. These pathogens can be transmitted through contaminated food or water, person-to-person contact, or contact with contaminated surfaces. The severity can range from mild discomfort lasting a day or two to severe dehydration requiring hospitalization.

In developed countries, viral gastroenteritis is the most common form, with norovirus and rotavirus being the primary culprits. Bacterial causes include Salmonella, E. coli, Campylobacter, and Shigella, often associated with foodborne illness. While most cases resolve on their own with supportive care, severe cases can lead to dangerous complications, particularly dehydration, making prompt recognition and appropriate management essential.

Symptoms

The symptoms of infectious gastroenteritis typically begin suddenly and can vary in severity depending on the causative agent and individual factors. Most symptoms appear within hours to a few days after exposure to the infectious agent.

Primary Gastrointestinal Symptoms

Systemic Symptoms

Signs of Dehydration

  • Dry mouth and throat
  • Decreased urination or dark urine
  • Dizziness or lightheadedness
  • Rapid heartbeat
  • Sunken eyes
  • Dry, cool skin
  • Extreme thirst
  • Fluid retention paradoxically in some cases

Severe Symptoms Requiring Immediate Care

  • Persistent vomiting preventing fluid intake
  • Signs of severe dehydration
  • Blood in vomit (hematemesis)
  • High fever (over 102°F/39°C)
  • Severe abdominal pain
  • Confusion or altered mental state
  • No urination for 8+ hours
  • Rapid weight loss

Causes

Infectious gastroenteritis can be caused by various pathogens, each with different transmission methods, incubation periods, and clinical presentations.

Viral Causes (60-70% of cases)

  • Norovirus:
    • Most common cause in adults
    • Highly contagious
    • Spreads through contaminated food, water, surfaces
    • Common in cruise ships, schools, nursing homes
  • Rotavirus:
    • Leading cause in young children worldwide
    • Vaccine-preventable
    • Fecal-oral transmission
    • Seasonal peaks in temperate climates
  • Adenovirus:
    • Types 40 and 41 cause gastroenteritis
    • More common in children
    • Can cause prolonged symptoms
  • Astrovirus:
    • Mild symptoms
    • Common in young children and elderly

Bacterial Causes (15-20% of cases)

  • Salmonella:
    • From contaminated eggs, poultry, unpasteurized dairy
    • Can cause typhoid fever (S. typhi)
  • Campylobacter jejuni:
    • Most common bacterial cause
    • From undercooked poultry, unpasteurized milk
  • E. coli:
    • Several pathogenic strains
    • EHEC can cause hemolytic uremic syndrome
    • From contaminated beef, produce, water
  • Shigella:
    • Causes dysentery
    • Person-to-person transmission
    • Common in daycare settings
  • Clostridium difficile:
    • Associated with antibiotic use
    • Healthcare-associated infections

Parasitic Causes (Less common)

  • Giardia lamblia: From contaminated water sources
  • Cryptosporidium: Resistant to chlorination
  • Entamoeba histolytica: Causes amoebic dysentery

Transmission Routes

  • Fecal-oral route (most common)
  • Contaminated food or water
  • Person-to-person contact
  • Contact with contaminated surfaces
  • Airborne particles from vomiting (norovirus)

Risk Factors

Several factors increase the risk of developing infectious gastroenteritis:

  • Age extremes:
    • Young children (immature immune systems)
    • Elderly adults (weakened immunity)
  • Weakened immune system:
    • HIV/AIDS
    • Chemotherapy patients
    • Organ transplant recipients
    • Chronic diseases
  • Environmental factors:
    • Living in crowded conditions
    • Daycare attendance
    • Institutional settings (nursing homes, hospitals)
    • Poor sanitation
  • Travel:
    • International travel to developing countries
    • Cruise ship travel
    • Camping with untreated water exposure
  • Seasonal factors:
    • Rotavirus peaks in winter/spring
    • Bacterial infections more common in summer
  • Medications:
    • Antibiotics (C. difficile risk)
    • Proton pump inhibitors
    • Immunosuppressants
  • Dietary habits:
    • Consuming raw or undercooked foods
    • Unpasteurized dairy products
    • Contaminated water

Diagnosis

Most cases of infectious gastroenteritis are diagnosed based on clinical presentation and don't require extensive testing. However, specific tests may be needed in severe cases or outbreaks.

Clinical Assessment

  • Medical history including:
    • Symptom onset and duration
    • Recent travel
    • Food consumption history
    • Sick contacts
    • Medication use
  • Physical examination:
    • Vital signs (temperature, blood pressure, pulse)
    • Hydration status assessment
    • Abdominal examination
    • Skin turgor and mucous membranes

Laboratory Tests

  • Stool tests:
    • Culture for bacteria
    • Ova and parasites examination
    • Viral antigen detection
    • PCR testing for specific pathogens
    • C. difficile toxin assay
  • Blood tests:
    • Complete blood count
    • Electrolytes and kidney function
    • Inflammatory markers (CRP, ESR)
    • Blood cultures if bacteremia suspected

When Testing is Indicated

  • Severe dehydration
  • Bloody diarrhea
  • High fever
  • Prolonged symptoms (>7 days)
  • Immunocompromised patients
  • Outbreak investigations
  • Recent antibiotic use
  • Travel-associated diarrhea

Treatment Options

Treatment of infectious gastroenteritis focuses primarily on preventing dehydration and managing symptoms. Most cases resolve without specific therapy.

Fluid and Electrolyte Replacement

  • Oral rehydration:
    • Oral rehydration solutions (ORS)
    • Clear liquids (broth, electrolyte drinks)
    • Avoid sugary drinks and caffeine
    • Small, frequent sips if vomiting
  • Intravenous fluids:
    • For severe dehydration
    • Unable to tolerate oral fluids
    • Electrolyte replacement

Dietary Management

  • During acute phase:
    • Clear liquids initially
    • BRAT diet (bananas, rice, applesauce, toast)
    • Avoid dairy, fatty foods, caffeine
    • Small, frequent meals
  • Recovery phase:
    • Gradual return to normal diet
    • Probiotics may help
    • Continue avoiding irritating foods

Medications

  • Generally not recommended:
    • Anti-diarrheal drugs (may prolong infection)
    • Antiemetics (use cautiously)
  • Specific situations:
    • Antibiotics for specific bacterial infections
    • Antiparasitics for parasitic causes
    • Probiotics for C. difficile
    • Zinc supplementation in children

When Antibiotics Are Indicated

  • Confirmed Shigella, Salmonella typhi
  • Severe Campylobacter infection
  • C. difficile colitis
  • Traveler's diarrhea with severe symptoms
  • Immunocompromised patients

Supportive Care

  • Rest and avoid strenuous activity
  • Good hygiene to prevent spread
  • Isolation precautions if hospitalized
  • Monitor for complications

Prevention

Preventing infectious gastroenteritis involves multiple strategies to reduce exposure to pathogens:

Personal Hygiene

  • Hand hygiene:
    • Wash hands with soap and water for 20 seconds
    • Especially after using bathroom and before eating
    • Hand sanitizer less effective against some viruses
  • Personal practices:
    • Avoid touching face with unwashed hands
    • Don't share personal items
    • Stay home when sick

Food Safety

  • Food preparation:
    • Cook foods to safe temperatures
    • Avoid cross-contamination
    • Refrigerate promptly
    • Wash fruits and vegetables
  • Food choices:
    • Avoid raw or undercooked meats, eggs
    • Pasteurized dairy products only
    • Be cautious with shellfish

Water Safety

  • Drink treated or boiled water when traveling
  • Avoid ice in developing countries
  • Use bottled water for brushing teeth if needed
  • Avoid swallowing water while swimming

Vaccination

  • Rotavirus vaccine: Part of routine childhood immunizations
  • Typhoid vaccine: For travelers to endemic areas
  • Hepatitis A vaccine: Prevents one cause of gastroenteritis

Environmental Measures

  • Disinfect contaminated surfaces
  • Proper disposal of diapers and waste
  • Chlorinate swimming pools adequately
  • Improve sanitation facilities

When to See a Doctor

While most cases resolve on their own, medical attention is necessary in certain situations:

  • Signs of severe dehydration
  • Blood in stool or vomit
  • High fever (over 102°F/39°C)
  • Severe abdominal pain
  • Symptoms lasting more than 3 days
  • Unable to keep fluids down for 24 hours
  • Decreased urination
  • Dizziness or fainting

High-risk groups requiring earlier medical attention:

  • Infants and young children
  • Elderly adults
  • Pregnant women
  • People with chronic illnesses
  • Immunocompromised individuals

Emergency symptoms requiring immediate care:

  • Confusion or altered mental state
  • Severe dehydration symptoms
  • Persistent vomiting preventing any fluid intake
  • Signs of shock (rapid pulse, low blood pressure)
  • Severe abdominal distension

Frequently Asked Questions

How long is gastroenteritis contagious?

The contagious period varies by cause. Viral gastroenteritis can be contagious from before symptoms start until several days after recovery. Norovirus can be shed in stool for up to 2 weeks after recovery.

Can you get gastroenteritis twice?

Yes, you can get gastroenteritis multiple times because there are many different viruses and bacteria that cause it. Immunity to one strain doesn't protect against others.

Is the stomach flu the same as influenza?

No, despite the name "stomach flu," gastroenteritis is not related to influenza, which is a respiratory illness. The term is a misnomer that has become common usage.

What's the difference between food poisoning and gastroenteritis?

Food poisoning is a type of gastroenteritis specifically caused by contaminated food. The symptoms are similar, but food poisoning often affects multiple people who ate the same food and symptoms typically start within hours.

When can I return to work or school?

Generally, you should wait at least 48 hours after symptoms have stopped before returning to work or school, especially if you work in food service, healthcare, or with children.

References

  1. Bresee JS, et al. The Management of Acute Gastroenteritis in Young Children. MMWR Recomm Rep. 2023;52(RR-16):1-16.
  2. World Health Organization. Diarrhoeal disease. WHO Fact Sheet. 2023.
  3. Guarino A, et al. European Society for Pediatric Gastroenterology, Hepatology, and Nutrition/European Society for Pediatric Infectious Diseases Evidence-Based Guidelines for the Management of Acute Gastroenteritis in Children in Europe. J Pediatr Gastroenterol Nutr. 2014;59(1):132-152.
  4. Shane AL, et al. 2017 Infectious Diseases Society of America Clinical Practice Guidelines for the Diagnosis and Management of Infectious Diarrhea. Clin Infect Dis. 2017;65(12):e45-e80.
  5. Centers for Disease Control and Prevention. Viral Gastroenteritis. CDC Guidelines. 2023.

Medical Disclaimer: This information is for educational purposes only and should not replace professional medical advice. Always consult with a qualified healthcare provider for diagnosis and treatment of any medical condition.