Stomach Flu
Gastroenteritis (stomach flu) is a common intestinal infection causing diarrhea, vomiting, and abdominal cramps. While usually self-limiting within 2-10 days, severe dehydration can occur. Proper hydration and rest are essential for recovery. Most cases are viral and don't require antibiotics.
Get Expert Care Today
What Is Stomach Flu?
Gastroenteritis (stomach flu) is inflammation of the stomach and intestines caused by viral, bacterial, or parasitic infection. Despite its name, it's not related to influenza, which affects the respiratory system. Stomach flu causes diarrhea, vomiting, abdominal cramps, and sometimes fever.
Most cases are viral and self-limited, resolving within 2-10 days with supportive care. The main concern is dehydration, which can be serious, especially in young children, elderly, and immunocompromised individuals. Some bacterial infections may require antibiotics.
At MyDoc Urgent Care, we rapidly assess gastroenteritis severity, identify concerning findings, provide hydration support, and guide management for optimal recovery.
Typical Symptoms
Watery diarrhea (usually non-bloody)
Bloody diarrhea (suggests bacterial infection)
Abdominal pain or cramping
Nausea or vomiting
Loss of appetite
Low-grade fever (usually <101°F)
Muscle aches or body aches
Headache
Fatigue or weakness
Dehydration signs (dry mouth, thirst, dizziness)
Urgent need to use bathroom
Stomach bloating or gas
Viral Causes (Most Common)
Viruses cause most gastroenteritis cases. They're usually self-limited and don't require specific antiviral treatment.
Norovirus
Prevalence: One of the most common causes; ~50% of viral gastroenteritis outbreaks
Transmission: Direct contact, contaminated food/water, respiratory droplets, fecal-oral route
Duration: Usually 1-3 days; rarely >10 days
Typical Symptoms: Acute onset of watery diarrhea, vomiting, cramps; fever less common
Contagious Period: 48-72 hours from symptom onset; can shed virus longer
Rotavirus
Prevalence: Most common viral gastroenteritis in children worldwide; 40% of hospitalizations for gastroenteritis
Transmission: Fecal-oral route, direct contact, contaminated surfaces, fomites
Duration: Usually 3-8 days; averaging 5-7 days
Typical Symptoms: Watery diarrhea (often profuse), vomiting, fever (usually 38-39°C), abdominal pain
Contagious Period: Most contagious first 3-8 days; can shed for weeks in immunocompromised
Enteroviruses (Coxsackievirus, Echovirus)
Prevalence: 10-15% of viral gastroenteritis; more common in summer/fall
Transmission: Fecal-oral route, respiratory droplets, contaminated food/water
Duration: Usually 3-7 days
Typical Symptoms: Diarrhea, vomiting, abdominal pain, fever, rash possible (Coxsackie)
Contagious Period: 7-10 days; fecal shedding can continue for weeks
Adenovirus (Types 40, 41)
Prevalence: 5-15% of viral gastroenteritis in children
Transmission: Fecal-oral route, respiratory droplets, contaminated surfaces
Duration: Usually 1-2 weeks; longest duration among viral causes
Typical Symptoms: Watery diarrhea (often mild), vomiting, fever, mild respiratory symptoms
Contagious Period: While symptomatic and for 1-2 weeks after
Astrovirus
Prevalence: 2-10% of viral gastroenteritis; ~10% in children <2 years
Transmission: Fecal-oral route, direct contact, contaminated food/water
Duration: Usually 1-4 days; up to 9 days in immunocompromised
Typical Symptoms: Diarrhea, vomiting, abdominal cramps, fever, malaise
Contagious Period: While symptomatic; longer in immunocompromised
Sapovirus
Prevalence: 2-5% of viral gastroenteritis; similar to norovirus
Transmission: Fecal-oral route, respiratory droplets, contaminated food/water
Duration: Usually 1-4 days
Typical Symptoms: Watery diarrhea, vomiting, abdominal cramping, fever, malaise
Contagious Period: While symptomatic and 2-3 days after symptoms resolve
Bacterial Causes
Bacteria cause 10-20% of gastroenteritis. Symptoms often more severe; some require antibiotics.
Staphylococcus aureus
Prevalence: Common foodborne pathogen; 5-10% of bacterial gastroenteritis
Transmission: Contaminated food (especially dairy, meats, prepared foods)
Onset: 30 minutes to 6 hours (average 1-6 hours) - fastest of foodborne pathogens
Duration: Usually 1 day; rarely >24 hours (shortest duration)
Symptoms: Acute onset vomiting, nausea, abdominal cramps; diarrhea less common
Severity: Usually mild; severe cases rare
Salmonella species
Prevalence: Very common; 2-3 million cases/year in US; 5-10% of bacterial gastroenteritis
Transmission: Contaminated poultry, eggs, dairy, reptiles/turtles, fecal-oral
Onset: 6-72 hours after exposure (average 12-36 hours)
Duration: Usually 4-7 days
Symptoms: Fever (often >101°F), bloody diarrhea, abdominal cramps, vomiting
Severity: Usually moderate; can be severe in very young, elderly, immunocompromised
Shigella species
Prevalence: 10-15% of bacterial gastroenteritis; more common in children
Transmission: Fecal-oral route, contaminated food/water, direct contact, poor sanitation
Onset: 1-3 days after exposure (average 2 days)
Duration: Usually 5-7 days
Symptoms: Watery diarrhea progressing to bloody diarrhea, fever, severe cramps, tenesmus
Severity: Can be severe; high fever common
Enteropathogenic E. coli (EPEC)
Prevalence: 5-10% of bacterial gastroenteritis; more common in developing countries
Transmission: Contaminated food/water, fecal-oral route
Onset: 1-8 days after exposure
Duration: Usually 1-2 weeks; can be chronic
Symptoms: Watery diarrhea, low-grade fever, abdominal cramps, malaise
Severity: Usually mild to moderate; can be severe in infants
Enterotoxigenic E. coli (ETEC)
Prevalence: Leading bacterial cause of traveler's diarrhea; 5-10% of gastroenteritis cases
Transmission: Contaminated food/water, poor sanitation
Onset: 1-3 days after exposure
Duration: Usually 3-5 days
Symptoms: Watery diarrhea (often profuse), abdominal cramps, nausea; usually no fever
Severity: Usually mild to moderate; can be severe with profuse diarrhea
Shiga toxin-producing E. coli (STEC/O157:H7)
Prevalence: 1-2% of bacterial gastroenteritis; but most dangerous
Transmission: Undercooked beef, contaminated produce, water, fecal-oral route
Onset: 1-8 days after exposure (average 3-4 days)
Duration: Usually 5-10 days
Symptoms: Bloody diarrhea (often profuse), severe cramps, little/no fever; vomiting rare
Severity: Can be severe; leading to hemolytic uremic syndrome
Campylobacter jejuni
Prevalence: One of the most common bacterial causes; 5-20% of bacterial gastroenteritis
Transmission: Undercooked poultry, contaminated water, unpasteurized dairy
Onset: 2-5 days after exposure (average 2-3 days)
Duration: Usually 5-7 days; can last 2-3 weeks
Symptoms: Bloody diarrhea, fever (often >101°F), severe abdominal cramps
Severity: Usually moderate; can mimic appendicitis
Vibrio species (V. cholerae, V. parahaemolyticus)
Prevalence: Rare in developed countries; common in coastal areas/developing countries
Transmission: Contaminated seafood, water
Onset: Hours to 5 days depending on species
Duration: Usually 3-7 days
Symptoms: Profuse watery diarrhea ("rice water" stools with V. cholerae), vomiting, cramping
Severity: Can be severe; V. cholerae can cause rapid severe dehydration/death
Clostridium difficile
Prevalence: Usually nosocomial; associated with antibiotic use
Transmission: Spores, contaminated surfaces, fecal-oral route
Onset: During or within weeks of antibiotic therapy
Duration: Variable; can be chronic/recurrent
Symptoms: Watery diarrhea, abdominal pain, fever, toxic megacolon possible
Severity: Usually mild to moderate; can be severe/fulminant
Parasitic Causes
Parasites cause 1-3% of gastroenteritis, especially in travelers and developing countries.
Giardia lamblia (Giardiasis)
Prevalence: 1-3% of gastroenteritis; most common parasitic cause in developed countries
Transmission: Contaminated water (hiking, camping), fecal-oral route, contaminated food
Onset: 3-7 days after exposure (can be 1-2 weeks)
Duration: Highly variable; can be acute or chronic lasting weeks-months
Symptoms: Watery diarrhea, steatorrhea (greasy stools), abdominal cramps, nausea, malabsorption
Treatment: Metronidazole or tinidazole
Entamoeba histolytica (Amebiasis)
Prevalence: 0.1-1% of gastroenteritis; more common in tropical areas
Transmission: Contaminated water, fecal-oral route, poor sanitation
Onset: 1-3 weeks after exposure
Duration: Variable; can be acute or chronic
Symptoms: Bloody diarrhea, abdominal pain, fever; may be asymptomatic
Treatment: Metronidazole for invasive disease
Cryptosporidium species
Prevalence: 0.5-2% of gastroenteritis; more common in immunocompromised
Transmission: Contaminated water, direct contact, fecal-oral route
Onset: 2-10 days after exposure
Duration: Usually 1-2 weeks in immunocompetent; weeks-months in immunocompromised
Symptoms: Watery diarrhea, abdominal cramps, nausea, malabsorption
Treatment: Supportive care in immunocompetent; antiretroviral therapy in AIDS
Who Is Most Vulnerable?
Certain groups have higher risk of gastroenteritis and more severe disease.
Age: Young Children (<5 years)
Risk Level: Very High - 2-3x higher risk than adults
Description: Most vulnerable age group; developing immune system
Severity: Often more severe; dehydration risk high
Complications: Severe dehydration, malnutrition, hospitalization common
Age: Older Adults (>65 years)
Risk Level: High - 2x higher risk than younger adults
Description: Immune system becomes less effective with age
Severity: Often more severe; complications common
Complications: Severe dehydration, electrolyte imbalance, acute kidney injury
Living in Group Settings
Risk Level: High - rapid spread in close quarters
Description: Close contact with infected individuals
Severity:
Complications:
Immunosuppression (HIV/AIDS)
Risk Level: Very High - 10-100x higher risk
Description: Severely weakened immune system
Severity: Often severe; chronic/recurrent infections common
Complications: Chronic diarrhea, malnutrition, sepsis, death
Immunosuppression (Chemotherapy/Transplant)
Risk Level: Very High - during active immunosuppression
Description: Immune system compromised by cancer treatment or transplantation
Severity: Can be severe; requires aggressive management
Complications: Sepsis, organ failure, death if untreated
Recent Antibiotic Use
Risk Level: Moderate - especially with fluoroquinolones/clindamycin
Description: Disruption of normal gut flora
Severity:
Complications: Antibiotic-associated diarrhea, C. difficile colitis
Travel to Developing Countries
Risk Level: High - 20-50% of travelers develop "traveler's diarrhea"
Description: Exposure to contaminated food/water with unfamiliar pathogens
Severity:
Complications:
Contaminated Food/Water
Risk Level: High when exposure occurs
Description: Direct exposure to foodborne or waterborne pathogens
Severity:
Complications:
Close Contact with Infected Person
Risk Level: High during acute illness; prolonged after symptoms resolve
Description: Direct transmission from symptomatic individual
Severity:
Complications:
Chronic Digestive Disorders
Risk Level: Moderate - altered gut barriers/flora
Description: Conditions affecting normal GI barriers or motility
Severity: May be more severe or prolonged
Complications: More likely to have severe symptoms or complications
How Gastroenteritis Is Diagnosed
Diagnosis is usually clinical. Testing is reserved for severe disease, persistent symptoms, or outbreak investigation.
Clinical Examination & History
Indication: All suspected gastroenteritis cases
Accuracy: N/A; clinical judgment guides management
Timing: Immediate; during first evaluation
Advantages: Rapid, cost-free, identifies severe cases needing urgent care
Limitations: Cannot determine specific pathogen or rule out other diagnoses
Stool Culture
Indication: Bloody diarrhea, high fever, signs of invasive infection, severe disease
Accuracy: 80-95% for bacterial causes; less sensitive if antibiotics given
Timing: Results in 24-72 hours
Advantages: Confirms bacterial diagnosis, identifies specific pathogen, guides antibiotic selection
Limitations: Slow; expensive; not helpful for viral causes; requires timed collection
Stool Ova and Parasites (O&P)
Indication: Diarrhea lasting >1-2 weeks, travel to endemic area, immunocompromised
Accuracy: 60-95% depending on technique and number of samples
Timing: Results in 24-48 hours
Advantages: Specific for parasitic causes, guides treatment
Limitations: Multiple samples needed for best sensitivity; expensive; requires expertise
Stool Testing for C. difficile
Indication: Diarrhea during/after antibiotics, suspected C. difficile colitis
Accuracy: 90-95% for toxin detection; higher for nucleic acid testing
Timing: Results in hours to overnight
Advantages: Rapid diagnosis of C. difficile, guides treatment
Limitations: Only test if diarrhea present; repeat testing not recommended
Stool White Blood Cell/Leukocyte Count
Indication: Assess for invasive diarrhea (inflammatory vs. non-inflammatory)
Accuracy: 70-80% for identifying invasive causes
Timing: Results in hours
Advantages: Quick assessment of inflammation, guides empiric treatment decisions
Limitations: Not specific; doesn't identify pathogen
Stool Antigen/PCR Testing
Indication: Suspected viral or specific parasitic causes
Accuracy: 85-95% depending on test and pathogen
Timing: Results in hours to overnight
Advantages: Rapid diagnosis of specific viral causes, high sensitivity
Limitations: Expensive; limited availability; not all pathogens tested
Electron Microscopy
Indication: Identifying viruses in stool (rarely used)
Accuracy: Very high but requires expertise
Timing: Results variable
Advantages: Can identify multiple viral pathogens
Limitations: Expensive, limited availability, requires expertise, not routinely used
Blood Culture
Indication: Fever >103°F, signs of sepsis, severe systemic illness
Accuracy: Very high but low yield (bacteremia rare)
Timing: Results in 24-72 hours
Advantages: Identifies invasive infection, guides antibiotic therapy
Limitations: Low yield; most gastroenteritis doesn't have bacteremia
Complete Blood Count (CBC)
Indication: Severe disease, signs of sepsis, suspected hemolytic uremic syndrome
Accuracy: Varies; reflects inflammation/severity
Timing: Results in hours
Advantages: Identifies systemic response, complications
Limitations: Non-specific; doesn't identify pathogen
Comprehensive Metabolic Panel (CMP)
Indication: Severe disease, signs of dehydration, significant vomiting
Accuracy: Very good for assessment of dehydration/electrolyte status
Timing: Results in hours
Advantages: Guides hydration therapy, identifies complications
Limitations: Doesn't identify pathogen; doesn't change acute management
Treatment Approaches
Most gastroenteritis is managed with supportive care. Hydration is the cornerstone of treatment.
Hydration - Oral Rehydration Solution (ORS)
Indication: Mild to moderate dehydration; preferred first-line treatment
Effectiveness: 90-95% effective for mild-moderate dehydration
Onset: Immediate; benefits felt within hours
Advantages: Oral, non-invasive, inexpensive, effective, convenient, fewer complications
Disadvantages: May not be tolerated if vomiting; requires frequent small drinks
Hydration - IV Fluids
Indication: Severe dehydration, shock, persistent vomiting preventing oral intake
Effectiveness: 99% effective for severe dehydration if managed appropriately
Onset: Immediate; rapid reversal of shock
Advantages: Rapid correction, essential for severe dehydration/shock, allows oral intake cessation
Disadvantages: Requires IV access, hospital admission, more complications possible
Dietary Management - BRAT Diet
Indication: Mild to moderate gastroenteritis; traditional recommendation
Effectiveness: Helps recovery; not specifically treating infection
Onset:
Advantages: Familiar, well-tolerated, easy to obtain
Disadvantages: Limited nutrition; not evidence-based; outdated recommendation
Dietary Management - Continued Breastfeeding
Indication: Infants with gastroenteritis
Effectiveness:
Onset: Continued breast milk feeding during illness
Advantages: Maintains hydration, nutrition, immune protection
Disadvantages: None; universally recommended
Dietary Management - Age-Appropriate Feeding
Indication: All pediatric and adult patients
Effectiveness:
Onset: Early return to normal diet appropriate for age
Advantages: Maintains nutrition, faster recovery, better outcomes than prolonged fasting
Disadvantages:
Anti-motility Agents
Indication: Limited use in gastroenteritis (generally not recommended)
Effectiveness: Reduces diarrhea but increases complication risk
Onset:
Advantages:
Disadvantages:
Anti-emetics (Anti-nausea medication)
Indication: Significant nausea/vomiting preventing oral intake
Effectiveness: 80-90% effective for nausea relief
Onset: 15-30 minutes for IV; 30-60 minutes for oral
Advantages: Allows oral hydration, reduces IV need, decreases hospital admission
Disadvantages: Cost, potential side effects, not addressing underlying cause
Antibiotics - Specific Bacterial Causes
Indication: Confirmed or strongly suspected bacterial infection
Effectiveness:
Onset:
Advantages:
Disadvantages:
Antibiotics - C. difficile Infection
Indication: Confirmed C. difficile toxin in stool + symptoms
Effectiveness: Vancomycin/fidaxomicin 90%+ effective; metronidazole 60-70%
Onset:
Advantages:
Disadvantages:
Antiparasitic Medications
Indication: Confirmed parasitic infection
Effectiveness: Varies; 85-95% for Giardia and Amebiasis
Onset:
Advantages:
Disadvantages:
Probiotics
Indication: Questionable benefit; some use for viral gastroenteritis
Effectiveness: Slight reduction in diarrhea duration (6-24 hours) in some studies
Onset:
Advantages:
Disadvantages:
Bismuth Subsalicylate
Indication: Mild non-inflammatory diarrhea; traveler's diarrhea prevention
Effectiveness: Reduces diarrhea duration by ~1 day; prevents diarrhea in ~65%
Onset:
Advantages:
Disadvantages:
Hydration is Key: The most important treatment for gastroenteritis is maintaining hydration. Oral rehydration solution (ORS) is preferred over plain water.
Most Cases Self-Limited: 80-90% of viral gastroenteritis resolves within 1-2 weeks with supportive care alone. Antibiotics are not helpful and can cause harm.
Avoid Anti-Motility Agents: Medications like loperamide should be avoided as they increase complication risks.
Preventing Gastroenteritis
Prevention focuses on hygiene, food safety, and breaking fecal-oral transmission.
Wash hands frequently with soap and warm water (20+ seconds, especially after bathroom/before eating)
Practice proper hand hygiene especially after using toilet or changing diapers
Do not share towels, washcloths, or personal items during acute illness
Clean and disinfect contaminated surfaces and bathrooms regularly
Avoid preparing food for others if you have gastroenteritis
Stay home from work/school/childcare during acute illness (at least 24 hours after diarrhea stops)
Do not share eating utensils, cups, or drinking containers
Separate bathroom use if possible when household member is ill
Cook foods to proper internal temperatures (use food thermometer)
Refrigerate perishable foods promptly; don't leave at room temperature >2 hours
Wash fruits and vegetables under running water before consuming
Avoid unpasteurized dairy products and raw/undercooked eggs
Avoid drinking untreated water when traveling (drink bottled/boiled water)
Avoid ice made from untreated water in developing countries
Wash hands after contact with animals, reptiles, or pets
Practice food safety: prevent cross-contamination of raw meats with other foods
Use separate cutting boards for raw meats and vegetables
Store raw meats on bottom shelf of refrigerator
Avoid buffets and street food in high-risk areas during travel
Get rotavirus vaccination if in age-appropriate range (infants)
Managing at Home
Most gastroenteritis can be managed at home with proper hydration and rest.
Rest: Allow body to recover; sleep helps immune response
Hydration is priority: Drink small frequent amounts of ORS or clear fluids
Avoid dehydration: Monitor urine color (pale yellow = good hydration)
Replace lost electrolytes: Use ORS, sports drinks, or coconut water
Eat light foods when ready: Toast, crackers, rice, bananas once hydration established
Gradually resume normal diet: Advance foods as symptoms improve
Avoid dairy temporarily: Gastroenteritis can cause temporary lactose intolerance
Avoid high-fat, spicy, high-fiber foods initially
Stay in cool environment: Fever will break on its own; no need to bundle
Use acetaminophen or ibuprofen for fever/aches if needed (follow dosing)
Breastfeed frequently if infant: Continue breastfeeding during illness
Monitor diaper output: Ensure adequate wet diapers in infants
Observe for dehydration signs: Thirst, dry mouth, dark urine, dizziness, weakness
Avoid close contact: Minimize spreading to family members
Practice hand hygiene: Wash hands frequently to prevent transmission
Get adequate fluid/electrolyte intake even if not hungry
Avoid alcohol and caffeine: Can worsen diarrhea/dehydration
Avoid dairy initially: Risk of temporary lactose intolerance
Most cases self-limited: Improve within 1-2 weeks
Follow up if not improving: Seek medical care if no improvement after 10 days
When to Seek Medical Care
Seek immediate medical attention if you experience these warning signs.
Severe Dehydration Signs
Extreme thirst, dark urine, dizziness, confusion, lethargy, dry mouth/lips
Bloody Diarrhea
Indicates possible invasive infection or severe intestinal injury
Severe Abdominal Pain
Persistent severe cramping may indicate complications like perforation
Fever >103°F
High fever may indicate invasive infection or severe disease
Persistent Vomiting
Unable to keep any fluids down for >6 hours; prevents hydration
Signs of Sepsis
Fever with confusion, rapid heart rate, rapid breathing, hypotension
Blood in Vomit
Hematemesis suggests upper GI bleeding or severe inflammation
Abdominal Distention
Severe bloating or distention may suggest toxic megacolon
Severe Headache
May indicate meningitis if accompanied by fever and neck stiffness
Altered Mental Status
Confusion or lethargy suggests severe infection or severe dehydration
Gastroenteritis Usually Improves on Its Own: Most cases resolve within 1-2 weeks with supportive care. The focus is on preventing dehydration and complications.
Hydration is Critical: Especially in young children, elderly, and immunocompromised individuals. Severe dehydration can be dangerous and requires urgent medical attention.
Most Don't Need Antibiotics: 80-90% of cases are viral. Antibiotics don't help and can cause harm. Specific bacteria are treated when identified.
At MyDoc Urgent Care, we assess gastroenteritis severity, provide IV hydration if needed, evaluate for complications, and manage symptoms. We're available at convenient locations in Forest Hills, East Meadow, Brooklyn, Bronx, Jackson Heights, and Little Neck for expert evaluation and care when you need it.