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What virus starts with diarrhea?

Diarrhea can be caused by a variety of viruses that infect the gastrointestinal tract. Some common viral causes of diarrhea include norovirus, rotavirus, astrovirus, adenovirus, and sapovirus. Let’s take a closer look at each of these viruses and how they lead to diarrhea.


Norovirus is one of the most common causes of acute gastroenteritis and diarrhea in adults and children. It is extremely contagious and spreads easily from person to person, as well as via contaminated food or water. Norovirus infection often begins suddenly with vomiting, followed by watery diarrhea a day or two later. Other symptoms may include nausea, stomach pain, fatigue, and low-grade fever. Norovirus diarrhea usually lasts 1-3 days and most people recover fully without complications. Good hygiene, like handwashing, is important to prevent norovirus infection.


Rotavirus is the leading cause of severe diarrhea in infants and young children worldwide. By age 5, nearly every child will have had at least one rotavirus infection. Rotavirus spreads by the fecal-oral route, meaning through contact with stool from an infected person. It initially infects the small intestine and can lead to watery diarrhea, vomiting, fever, and abdominal pain. Rotavirus diarrhea typically lasts 3-8 days. Severe cases can result in dehydration, which may require hospitalization to correct. A vaccine is available to prevent rotavirus infection.


Astroviruses are a group of viruses that cause gastroenteritis, predominantly in children under the age of 2 and immunocompromised individuals. They account for up to 10% of all cases of viral diarrhea in children. Astrovirus infection causes watery diarrhea lasting 2-4 days, along with vomiting, fever, headache, and abdominal pain. Most people recover fully in a few days with only supportive treatment to correct dehydration. Person-to-person contact is the primary mode of transmission for astroviruses.


Adenoviruses can cause a wide range of illnesses, including common cold symptoms, pink eye, cough, and diarrhea. There are over 50 different types of adenoviruses that can infect humans. Two types in particular, adenovirus 40 and 41, are well-known causes of acute gastroenteritis. Adenovirus diarrhea usually lasts 5-12 days and may be accompanied by vomiting, fever, and abdominal pain. This type of viral diarrhea is more common in children, but adults can also be affected. The virus spreads through close contact, fecal-oral transmission, or consumption of contaminated water.


Sapovirus is a cause of gastroenteritis similar to norovirus. It can affect people of any age but is more common in children under 5 years old. The main symptoms are diarrhea, vomiting, nausea, and abdominal discomfort. Sapovirus diarrhea typically lasts 1-4 days and is usually self-limiting. Dehydration may occur, especially in young children and the elderly. Sapovirus spreads easily from person to person or via contaminated surfaces and food. Proper hygiene is important to prevent transmission.

When to See a Doctor

In most cases, viral diarrhea is unpleasant but resolves on its own without medical intervention. However, dehydration is a serious concern, especially in infants, young children, the elderly, and those with compromised immune systems. See a doctor right away if you or a family member has:

  • Diarrhea for more than 2 days in babies under 6 months old
  • Diarrhea for more than 1 day in babies over 6 months old
  • Severe lack of energy, dizziness, or lightheadedness
  • No urine output for 6-8 hours
  • Bloody or black stools
  • High fever over 102°F (39°C)
  • Signs of dehydration like excessive thirst, dry mouth, decreased urination, or sunken eyes

Seeking prompt medical care for dehydration can prevent serious complications. Doctors can provide IV fluids and electrolyte replacement if needed.

Diagnosing Viral Diarrhea

To determine the exact cause of diarrhea, doctors may:

  • Ask about symptoms and medical history
  • Perform a physical exam to check for dehydration
  • Order stool tests to identify viruses
  • Test blood to look for signs of infection

Stool cultures are often used to detect viruses like norovirus, rotavirus, and adenovirus that can cause diarrhea. Newer rapid diagnostics are also available to quickly identify viruses within 1-2 hours.

Treating Viral Diarrhea

There are no specific medications that can cure or treat viral diarrhea. The main goals of treatment are to prevent and correct dehydration and manage symptoms. Steps for treatment may include:

  • Drinking plenty of fluids, like water, broths, or oral rehydration solutions
  • Getting rest
  • Eating bland foods as tolerated once vomiting subsides
  • Taking over-the-counter anti-diarrheal or anti-nausea medication
  • Seeking medical care for IV fluids if severely dehydrated

Preventing dehydration is imperative. Infants and young children are at high risk and need especially close monitoring.

Preventing Viral Diarrhea

Practicing good hygiene is the best way to prevent viral diarrhea. Steps to take include:

  • Washing hands thoroughly with soap and water after using the bathroom, changing diapers, before eating, and after contact with sick individuals
  • Disinfecting surfaces and toys in childcare settings
  • Avoiding close contact with symptomatic people
  • Staying home from work, school, or childcare when ill
  • Exercising caution when traveling to developing countries where hygiene may be poor
  • Avoiding potentially contaminated food and water
  • Getting vaccinated for rotavirus

Proper food safety techniques, like cooking meats thoroughly and washing produce, can also help prevent foodborne viral illness.

Risk Factors for Severe Infection

Most healthy people recover quickly from viral diarrhea with only supportive treatment. However, certain groups are at increased risk of severe dehydration and complications. Risk factors include:

  • Infants and young children under 5 years old
  • Adults over age 65
  • Pregnancy
  • Weakened immune system from illness or medication
  • Chronic medical conditions like diabetes, kidney disease, and inflammatory bowel disease
  • Poor access to clean drinking water and medical care

Taking steps to prevent dehydration and promptly treating diarrhea in high-risk individuals is essential.

Common Complications

Most cases of viral diarrhea resolve without complications within a few days. However, some potential complications include:

  • Dehydration: Excessive fluid loss can lead to electrolyte imbalances, kidney problems, hypotension, and shock.
  • Malnutrition: Inability to absorb nutrients from food due to prolonged diarrhea.
  • Severe infections: Immunocompromised individuals may suffer disseminated viral disease causing organ impairment.
  • Hemolytic uremic syndrome (HUS): A rare complication linked to some viral infections that causes kidney failure.

Rapid treatment of dehydration can prevent progression to life-threatening complications. Seeking prompt medical attention for high-risk groups is vital.

Prognosis and Recovery

With appropriate treatment, most cases of viral diarrhea resolve within a few days without lasting effects. However, recovery time depends on factors like:

  • Age and health status of the individual
  • Degree of dehydration
  • How early treatment began
  • The particular virus involved
  • Whether complications like HUS develop

Healthy adults may recover fully in 1-3 days with only supportive self-care. But infants and the elderly may require hospitalization for IV fluid replacement, taking closer to a week to regain strength. Immunocompromised patients tend to suffer more severe and prolonged illness. If complications like HUS occur, full recovery can take weeks or months.


Diarrhea beginning with vomiting is most commonly caused by viruses like norovirus, rotavirus, astrovirus, adenovirus, and sapovirus. Preventing dehydration is key, with IV fluids sometimes needed for those most at risk. Practicing good hygiene, disinfecting surfaces, staying home when ill, and getting vaccinated are the best ways to avoid infection. While uncomfortable, viral diarrhea is generally self-limiting and patients can expect a full recovery within about 1-3 days in otherwise healthy individuals.