Stomach Flu

Symptoms

• Watery diarrhea: Frequent loose or liquid stools, usually without blood, that can quickly drain fluids and electrolytes.
• Nausea and vomiting: An urge to vomit and repeated vomiting that make it hard to keep food or liquids down.
• Abdominal cramps: Intermittent belly pain and cramping from irritation of the stomach and intestines.
• Low-grade fever: A mild fever and chills as the body fights the infection; high or persistent fever is less typical and warrants closer attention.
• Muscle aches and headache: General body aches, headache, and fatigue that often come with a viral gut infection.
• Loss of appetite: Reduced desire to eat or drink, which can worsen fluid loss if it lasts more than a day.

When it's an emergency

Come straight to Bellaire ER — open 24/7 — if you or someone you care for shows signs of severe dehydration (call 911 if they are fainting, confused, or too weak to travel safely): little or no urination for 8 or more hours, very dark urine, extreme thirst, dizziness or fainting when standing, a rapid heartbeat, sunken eyes, or unusual drowsiness, confusion, or weakness.

Seek emergency care if you cannot keep any liquids down for more than 24 hours, if vomiting or diarrhea lasts more than two to three days, or if you see blood in your vomit or stool or black, tarry stools.

Other red flags that need an ER include a fever above 103 degrees Fahrenheit, severe or constant abdominal pain (especially pain focused in the lower right belly, which can signal appendicitis rather than stomach flu), a stiff neck with severe headache, or signs of dehydration in an infant, older adult, pregnant person, or anyone with a weakened immune system.

When fluid loss is severe, drinking is often not enough. Bellaire ER can restore fluids and electrolytes quickly with IV therapy and rule out more serious causes on site.

When it's not an emergency

Most stomach flu is mild and gets better on its own in one to three days. If you can sip fluids and keep some down, are urinating normally, and have no warning signs, you can usually recover at home with rest, small frequent sips of water or an oral rehydration solution, and a gradual return to bland foods.

Bellaire ER's virtual urgent care is a reasonable first step for mild symptoms. A clinician can confirm it is likely viral, suggest over-the-counter measures, and tell you which warning signs should prompt an in-person visit. Bellaire ER offers telemedicine for exactly these situations.

Your primary care doctor is also appropriate for mild, stable symptoms or for a young child or older adult who is drinking and alert. If symptoms worsen or you develop any of the red flags above, move up to emergency care.

What else could be causing this

Norovirus

The most common cause of gastroenteritis in adults, and the usual culprit behind outbreaks on cruise ships, in schools and in restaurants. Vomiting tends to dominate over diarrhea, onset is abrupt, and it typically runs its course in one to three days. Alcohol hand gel does not reliably kill it, which is why it spreads through a household so readily.

Rotavirus

The leading cause of severe gastroenteritis in infants and young children before routine vaccination. Watery diarrhea is the dominant symptom and can last five to seven days, long enough that dehydration becomes the real problem rather than the virus itself. Routine infant vaccination has made it far less common in the United States.

Bacterial food poisoning

Salmonella, Campylobacter, Shigella and some strains of E. coli, picked up from undercooked meat or poultry, unpasteurized dairy, or contaminated produce. These more often produce fever and blood or mucus in the stool than a virus does, and the illness tends to last longer. Blood in the stool is the feature that moves this up the list.

Preformed bacterial toxin

Staphylococcus aureus or Bacillus cereus growing in food that sat out, usually rice, dairy or prepared salads. The toxin is already in the food, so vomiting begins within one to six hours of eating rather than a day later, and it usually settles within a day. The short interval between the meal and the symptoms is the clue.

Clostridioides difficile and antibiotic-associated diarrhea

Diarrhea that begins during or in the weeks after a course of antibiotics, which disrupt the normal gut bacteria. C. difficile can cause watery diarrhea with cramping, fever and a markedly raised white cell count, and it needs specific treatment rather than waiting it out. Recent antibiotics change the approach, so mention them.

Appendicitis

Early appendicitis is mistaken for a stomach bug regularly, because nausea, vomiting and loss of appetite come first. What separates it is pain: it localizes to the lower right abdomen, becomes steadily worse rather than easing between episodes, and hurts more on movement or coughing. Diarrhea-dominant illness with pain that is settling in one spot is evaluated, not waited out.

Bowel obstruction

A mechanical blockage of the intestine, more likely after previous abdominal surgery or with a hernia. Vomiting is persistent and may turn bilious or feculent, the abdomen distends, and crucially gas and stool stop passing altogether — the opposite of gastroenteritis. This is a surgical problem, not an infection.

Urinary tract and kidney infection

Pyelonephritis commonly presents with vomiting, fever and malaise, and in older adults the urinary symptoms can be absent entirely. Flank or back tenderness alongside the nausea points this way. It is a frequent reason a presumed stomach bug turns out to be something else on a urine test.

Diabetic ketoacidosis

In someone with diabetes, vomiting with abdominal pain, deep rapid breathing, thirst and heavy urination can be ketoacidosis rather than a gut infection — and gastroenteritis itself can precipitate it. Anyone with diabetes who cannot keep fluids or medication down is evaluated urgently rather than managed at home.

What happens when you arrive

When you arrive at Bellaire ER with stomach flu symptoms, a board-certified emergency physician checks for dehydration and any signs of a more serious problem.

Care often includes intravenous (IV) fluids to rehydrate you and restore electrolytes, along with anti-nausea and anti-diarrheal medication to help you feel better faster. On-site labs can check your electrolytes, kidney function, and blood counts.

Because vomiting and diarrhea can occasionally point to something other than a virus, we can use our on-site CT, X-ray, and ultrasound to rule out conditions such as appendicitis, a bowel obstruction, or a kidney infection when your exam suggests it.

We diagnose and treat in a single visit, and most patients go home the same day without a hospital transfer. Before you leave, your physician explains your results, gives clear instructions on fluids and diet, and tells you which symptoms should bring you back.

Tests we can run on site

Basic metabolic panel

Measures sodium, potassium, chloride, bicarbonate, glucose and kidney function. It shows how much fluid and electrolyte you have actually lost, whether the kidneys are feeling it, and whether there is an acid-base problem that points away from a simple virus.

Complete blood count

A white cell count that is markedly raised, or a shift in the cell types, raises the possibility of a bacterial infection or an inflamed appendix rather than a virus. The red cell values also help judge concentration from dehydration.

Urinalysis

Checks for a urinary tract or kidney infection masquerading as a stomach bug, and for ketones and concentration that reflect how dehydrated you are. It is a small test that redirects the diagnosis often enough to be routine.

Stool testing

Used when the diarrhea is bloody, has lasted beyond a few days, follows antibiotics, or comes after travel. It identifies bacterial causes, parasites and C. difficile, which change treatment from fluids alone to specific therapy.

Pregnancy test

Run for anyone of childbearing age with vomiting and abdominal pain. It is not about the nausea itself; it rules out an ectopic pregnancy and changes which imaging is appropriate.

Ultrasound

Sound-wave imaging at the bedside, without radiation. It looks at the gallbladder, the kidneys and the appendix, and it is often the first imaging used in children and in pregnancy for exactly that reason.

CT scan

Cross-sectional imaging of the abdomen, used when the exam points to something structural — appendicitis, an obstruction, diverticulitis or an abscess. It answers the question a plain film cannot, which is what is actually happening inside the abdomen.

Treated here, or transferred

Bellaire ER is a licensed freestanding emergency room: board-certified emergency physicians and nurse practitioners, on-site CT, X-ray, ultrasound and laboratory, medication administered during your visit, open 24 hours a day, 365 days a year, for adults and children. It is equipped to evaluate, stabilize and treat, and it is not a hospital. Most gastroenteritis belongs squarely in the first category.

What is treated here is the dehydration and the symptoms driving it. Intravenous fluids replace what vomiting and diarrhea have taken out, and they work when sipping does not. Anti-nausea medication given through the IV often breaks the cycle in which every mouthful of fluid comes straight back up, which is the practical reason home rehydration fails. Electrolyte abnormalities found on the blood work are corrected, and any medication you need to continue at home is written as a prescription for you to fill at your own pharmacy.

Some causes are not treated here. A bowel obstruction, appendicitis or another surgical cause needs an operating room, and a freestanding emergency room has none. The same is true of a patient who needs admission for continued intravenous fluids, severe kidney injury, or diabetic ketoacidosis requiring an insulin infusion. In those cases the work starts here — the imaging, the labs, the fluids, the antibiotics where they are indicated — and continues without a gap during transfer to a hospital that has the service required. Transfer is a normal part of how a freestanding emergency room works, not a sign the visit went wrong.

If the evaluation points to a virus and you are rehydrated and keeping fluids down, your physician explains what was ruled out, how to manage the next few days, and which symptoms should bring you back.

Children

Bellaire ER treats adults and children. In young children the virus is rarely the danger; the fluid loss is. Children dehydrate faster than adults because they lose a larger share of their body water in the same number of episodes, and an infant can go from mildly unwell to significantly dehydrated within hours.

The signs to watch for in an infant or toddler are fewer than normal wet diapers — none in six to eight hours is a red flag — no tears when crying, a dry mouth, a sunken soft spot on the head, sunken eyes, and a child who is floppy, unusually sleepy, or difficult to rouse. A child who refuses all fluids, or who vomits back every attempt, needs to be seen rather than monitored at home. Any infant under three months with a rectal temperature of 100.4 degrees Fahrenheit or higher is an emergency evaluation regardless of the gut symptoms.

Oral rehydration solution is what children should be offered, in small frequent amounts — a teaspoon or two every few minutes is more effective than a cup they will bring straight back. Plain water alone, sports drinks, juice and soda are poor substitutes because the sugar and salt balance is wrong and can make the diarrhea worse. Over-the-counter anti-diarrheal medicines are not given to young children.

Bring a child in for green or bile-stained vomit, blood in the stool, a swollen or very tender abdomen, episodes of inconsolable crying with drawing up of the legs, or diarrhea lasting beyond a week. On-site laboratory testing and ultrasound are used in children first, before CT, when imaging is needed at all.

After you leave

Recovery from viral gastroenteritis is usually gradual rather than sudden. Vomiting typically settles before the diarrhea does, and loose stools can continue for several days after you feel broadly better. Mild cramping and a poor appetite for a few days are expected. Fatigue that outlasts the gut symptoms by a week is common and not in itself a worry.

Keep drinking even after you feel improved, in small amounts frequently rather than large glasses at once. An oral rehydration solution replaces salts as well as water, which plain water does not. Return to food when you want it, starting with bland, simple things, and do not force a strict diet — eating normally as tolerated is reasonable. Hold off on alcohol, caffeine and large fatty meals for a few days.

Come back, or call 911 if you cannot travel safely, if you cannot keep any fluids down again, if you stop urinating or urinate only small amounts of very dark urine, or if you become lightheaded on standing, confused or unusually drowsy. Return for blood in the vomit or stool, black tarry stools, a fever above 103 degrees Fahrenheit, or abdominal pain that becomes severe, constant, or settles into one spot — particularly the lower right. Pain that is getting worse while the diarrhea is getting better is a change worth having looked at again.

Take any medication you were given as directed and finish a course of antibiotics if one was prescribed. Book the follow-up you were advised to book, and if a stool test was sent, make sure you learn the result rather than assuming no news is good news.

Lowering your risk

Stomach flu spreads easily, especially the norovirus that causes many outbreaks. Wash your hands thoroughly with soap and water after using the bathroom and before preparing or eating food; alcohol hand sanitizer helps but does not reliably kill norovirus.

Disinfect contaminated surfaces, wash soiled laundry on hot, and avoid preparing food for others while you are sick and for two days after symptoms stop. Handle and cook food safely and rinse fruits and vegetables to lower the risk of foodborne illness. A rotavirus vaccine is routinely given to infants to prevent one common cause in young children.