Gastroenteritis / Stomach Bug: Symptoms, Causes, and When to Seek Medical Care
Gastroenteritis (Stomach bug or Stomach flu)
Gastroenteritis, often called a stomach bug or stomach flu, is irritation or inflammation of the stomach and intestines. It commonly causes nausea, vomiting, diarrhea, stomach cramps, and sometimes fever.
Despite the nickname “stomach flu,” gastroenteritis is not the same as influenza, which is a respiratory virus. A stomach bug usually affects the digestive system.
What is gastroenteritis?
Gastroenteritis can be caused by viruses, bacteria, parasites, foodborne illness, contaminated water, or close contact with someone who is sick. Viral gastroenteritis is common and can spread easily through contact with tiny particles of stool or vomit from an infected person. Watery diarrhea, abdominal pain or cramping, nausea or vomiting, and sometimes fever as common symptoms of viral gastroenteritis.
Norovirus is one common cause of stomach bug outbreaks. Norovirus can cause vomiting and diarrhea and can lead to dehydration, especially when fluid losses are significant.
Common causes
Gastroenteritis may be caused by:
Norovirus or other viruses
Contaminated food or water
Food poisoning
Close contact with someone who is sick
Poor hand hygiene after bathroom use or diaper care
Undercooked meat, seafood, poultry, or eggs
Unwashed fruits or vegetables
Recent travel
Parasites
Certain bacteria such as Salmonella, E. coli, Campylobacter, or Shigella
Some medications or medical conditions that can mimic infection
Common symptoms
Symptoms may include:
Nausea
Vomiting
Watery diarrhea
Stomach cramps
Abdominal pain
Fever
Chills
Body aches
Headache
Fatigue
Decreased appetite
Weakness
Signs of dehydration
Symptoms may begin suddenly and can last from a day or two to several days depending on the cause.
Risk factors
Some people have a higher risk of dehydration or complications, including:
Adults over age 65
Pregnant people
People with diabetes
People with kidney disease
People with heart disease
People with weakened immune systems
People taking immune-suppressing medications
People with inflammatory bowel disease
People who cannot keep fluids down
People with significant vomiting or diarrhea
Dehydration symptoms to watch for
Dehydration is one of the most important concerns with vomiting and diarrhea. Dehydration symptoms such as extreme thirst, dry mouth, urinating less than usual, feeling tired, dark-colored urine, and decreased skin turgor.
Possible dehydration warning signs include:
Very little urination
Dark urine
Dizziness or lightheadedness
Dry mouth
Excessive thirst
Severe weakness
Fast heart rate
Confusion
Fainting
Inability to keep fluids down
When to seek medical care
Schedule a medical evaluation if you have:
Vomiting or diarrhea lasting more than 2 days
Diarrhea lasting more than several days
Fever
Symptoms of dehydration
Severe stomach cramps
Symptoms after eating recalled food
Symptoms after recent travel
Symptoms after possible food poisoning
Symptoms in pregnancy
Diabetes, kidney disease, heart disease, or immune suppression
Symptoms that improve then worsen again
Concern for medication-related diarrhea
Recurrent or persistent digestive symptoms
Adults should seek medical help for vomiting lasting more than two days, diarrhea lasting more than several days, bloody diarrhea, fever over 102°F, lightheadedness or fainting when standing, confusion, or stomach pain.
When to seek urgent or emergency care
Seek urgent or emergency care for:
Blood in stool
Black or tarry stool
Vomiting blood
Severe or worsening abdominal pain
Severe dehydration
Fainting
Confusion
Trouble breathing
Chest pain
Severe weakness
Persistent vomiting
High fever with worsening symptoms
Stiff neck
Severe headache
Signs of sepsis, such as fever, fast heart rate, confusion, extreme weakness, or low blood pressure symptoms
Rapidly worsening symptoms
Inability to keep liquids down for 24 hours, vomiting blood, dehydration symptoms, blood in bowel movements, severe stomach pain, and fever above 104°F as reasons to seek care.
Can telehealth help?
Yes. Telehealth can help review symptoms, timing, possible exposures, hydration concerns, risk factors, medication safety, work notes when appropriate, and whether testing or in-person care may be needed.
Telehealth may not be appropriate for severe dehydration, bloody stool, black stool, severe abdominal pain, persistent vomiting, fainting, confusion, pregnancy with significant symptoms, immune suppression with severe symptoms, or rapidly worsening illness.
Prevention and follow-up
General prevention and follow-up considerations include:
Handwashing after bathroom use and before food preparation
Careful food handling
Avoiding food preparation for others while sick
Cleaning contaminated surfaces
Avoiding shared utensils during illness
Staying home when actively vomiting or having diarrhea
Following workplace or food-service return policies
Seeking follow-up if symptoms persist, worsen, or return
CDC infection-control guidance for norovirus notes that food-service personnel with acute gastroenteritis symptoms should be excluded from duty and should not return until at least 48 hours after symptoms resolve, or longer if local health regulations require it.
Final thought
A stomach bug is common and often improves with time, but dehydration and more serious infections can occur. Bloody stool, severe abdominal pain, persistent vomiting, confusion, fainting, high fever, or symptoms of dehydration should be evaluated promptly.
This information is for educational purposes only and does not replace medical advice, diagnosis, or treatment. If you are experiencing severe symptoms, signs of infection, severe allergic reaction symptoms, trouble breathing, or a medical emergency, call 911 or go to the nearest emergency room.
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