Is Diarrhea Contagious?

Diarrhea is usually contagious when it is acute, meaning it comes on suddenly. Acute diarrhea is often caused by a microorganism such as a bacteria or virus. These microorganisms can be easily passed between people or even between animals and people. Chronic or long-lasting cases of diarrhea are more likely to have causes that are not contagious.

Diarrhea is defined as loose or watery stool that occurs three or more times per day.

This article covers infectious diarrhea, its types, causes, treatment, and prevention. It also discusses how you can tell if diarrhea is contagious and how long you can expect symptoms to last.

How Does Diarrhea Spread?

The most common causes of diarrhea are viral, bacterial, and parasitic infections. Infectious diarrheal diseases are contagious, meaning that they can be spread between people.

Diarrheal infections are typically spread through the fecal-oral route. This means fecal matter that has infectious particles in it gets on a surface or person. Things that people touch a lot like doorknobs, buttons, and counters can be easily contaminated.

If someone doesn't wash their hands after using the bathroom, they can spread the infection when they touch other people (for example, by shaking hands). Once the virus is on your hands, it can be easily transmitted to your mouth in a number of ways such as biting a fingernail or eating finger food. People can also catch infections that cause diarrhea if a sick person makes food for them.

Kids can get infectious diarrhea easily because they tend to put their hands and objects in their mouths.

Animals can also contaminate sources of water and surfaces with pathogens that spread infectious diarrhea. These illnesses can be transmitted easily when people don't wash their hands after touching an animal.

There are two terms you may hear that are associated with infectious diarrhea:

• Gastroenteritis refers to bacterial or viral infections that affect both the stomach and small/large intestines. These patients present with nausea, vomiting, and abdominal pain, as well as diarrhea.
• Dysentery refers to infectious or inflammatory diarrheal diseases that result in the frequent passage of smaller stools containing varying amounts of mucus and/or blood.

Infectious diarrhea often comes on quickly and does not last longer than a few days, though some illnesses may cause diarrhea that lasts a week or two.

Once the cause is found, most infectious diarrheal diseases can be treated. However, some types of infectious diarrhea are harder to treat. People may have diarrhea that lasts a long time and leads to complications.

Viral Causes

Viruses are the most common cause of diarrhea. There are four specific viruses that most often cause infectious diarrhea:

• Norovirus, also known as the "cruise ship virus," is the most common cause of gastroenteritis in the United States. It is called the "cruise ship virus" because close living quarters on a ship can hasten its spread, and because health officials are required to track any outbreaks that occur on a cruise ship.
• Globally, rotavirus is the most common cause of vaccine-preventable diarrhea in children under 5 years of age. It is responsible for approximately 28% of all diarrheal deaths worldwide.
• Adenoviruses include a family of more than 50 subtypes. Types 40 and 41 are primarily responsible for causing diarrhea in humans. (Other adenoviral subtypes include cold viruses.)
• Astroviruses are a common cause of diarrhea in the elderly, children, and people with compromised immune systems.

Infectious diarrhea caused by a virus is usually highly contagious.

Bacterial Causes

Bacterial diarrhea is a major contributor to illness and death worldwide. Although less common in the U.S. than viral diarrhea, bacterial diarrhea disorders more often lead to dysenteric disease due to the development of ulcers and inflammation in the intestines. Dysenteric disease is an infection that causes diarrhea containing blood or mucus.

These bacteria commonly cause infectious diarrheal disease:

• Salmonella enteritidis can cause diarrhea, fever, and abdominal cramps within 12 to 72 hours of consuming contaminated food or beverage.
• Escherichia coli (especially E. coli 0157) is spread through contaminated food and dairy products and can lead to a condition known as hemorrhagic colitis.
• Shigella is common both in the U.S. and around the world and can often cause bloody diarrhea, particularly in children of preschool age.
• Campylobacter is among the most common bacterial foodborne infections and can cause bloody diarrhea due to acute intestinal inflammation.
• Vibrio infection is often associated with eating raw seafood or sushi.
• Staphylococcus aureus can cause explosive diarrhea due to toxins released by the bacteria.
• Clostridioides difficile (C. difficile or C. diff) is unique in that the rise of the infection is frequently linked to prior or concurrent antibiotic use. Today, it is the most common cause of hospital-acquired diarrhea.
• Yersinia is a species of bacteria that can cause a number of different diseases in humans. Yersinia enterocollitica is a common cause of infectious diarrhea. In contrast, Yersinia pestis has been isolated as a primary cause of the bubonic plague. Humans typically encounter Yersinia species in dairy products.

Bacterial infections that cause diarrhea can spread quickly between people, but it's more common for people to get sick after drinking water or eating food that is contaminated.

Parasitic Causes

Protozoa are the primary cause of parasitic diarrhea both in the U.S. and around the world. These single-celled organisms come in many forms. Among the three most common causes of parasitic diarrhea:

• Giardia lamblia is passed through contaminated food or by person-to-person contact and can result in explosive diarrhea within two days of infection.
• Entamoeba histolytica is related to fecal-oral transmission and can cause bloody diarrhea as these invasive parasites bore their way into the intestinal wall.
• Cryptosporidium is known to cause both respiratory and gastrointestinal illness and is characterized by the development of watery stools.

Infectious diarrhea caused by parasites is usually transmitted through infected drinking water.

What Is Non-Infectious Diarrhea?

Diarrhea can also be non-infectious. People with medical conditions affecting the digestive, immune, or endocrine (hormone) systems can have diarrhea as a symptom. Diarrhea caused by these conditions cannot be spread to other people.

Medical conditions that can cause non-infectious diarrhea include:

• Irritable bowel syndrome (IBS)
• Inflammatory bowel disease (IBD)
• Celiac disease
• Microscopic colitis
• Medication reaction
• Hyperthyroidism
• Lactose intolerance

People with these conditions may have acute episodes of diarrhea when the disease flares up, or they may have chronic diarrhea that lasts a long time.

When to See a Healthcare Provider

For healthy people, occasional diarrhea usually doesn't last long and gets better on its own without causing major problems. However, diarrhea is the second leading cause of death in children in the developing world. It's also a major contributor to work absenteeism and loss of productivity in the United States' workforce.

The elderly, very young children, and people with compromised immune systems are especially vulnerable to diarrheal infections. They are at an increased risk of complications related to severe diarrhea including dehydration and the need for hospitalization and fluid management. These groups are also more likely to die from complications.

How Is Contagious Diarrhea Diagnosed?

Determining whether the diarrhea is infectious, how long it will last, relevant treatment, and preventing its spread, depends on the cause. This requires seeing a healthcare provider.

Because the symptoms of infectious diarrhea can be similar to non-infectious diarrhea, you may not be able to tell what you have based on how you feel. And if you have an infection that's causing diarrhea, you won't necessarily know which pathogen is causing it.

To diagnose infectious diarrhea, providers will gather information from a patient—such as whether they have been around sick people or traveled recently. They can also run a series of tests to identify the cause of diarrhea.

Finding out whether diarrhea is infectious or not has several steps:

• A stool culture is commonly used to diagnose bacterial infections. A PCR test run on stool is also used to detect C. difficile.
• A combination of microscopic and antigen-based tests can help identify protozoa in stool samples.
• Viral infections can be diagnosed by running a PCR test on a person's stool, blood, or other body fluids.

How Is Infectious Diarrhea Treated?

The treatment for diarrhea depends on the cause and how sick a person is.

Medications can treat infectious diarrheal diseases. For example, antibiotics and antivirals can treat bacterial and viral infections, respectively, while antimicrobial agents can treat diarrhea caused by protozoans.

Anti-diarrheal medications can be prescribed along with oral rehydration therapy to prevent or treat the loss of fluid from diarrhea. The fluid can also be delivered intravenously (through a vein) if the dehydration is especially severe.

You may have a fever with infectious diarrhea and feel sick. An over-the-counter (OTC) fever-reducing or pain-relieving medication may help.

How Is Contagious Diarrhea Prevented?

Here are a few tips for preventing diarrhea infections at home and while you're out:

• Practice frequent proper handwashing with hot water and soap or use an antibacterial handwash.
• Sanitize your bathroom, kitchen, and anywhere in your home where food is prepared and eaten.
• Thoroughly cook all poultry, meat, or shellfish and use a kitchen thermometer to ensure the foods reach appropriate internal temperatures.
• Clean all cutting boards and utensils immediately after coming into contact with raw meat, poultry, or seafood.
• Wash all fruits and vegetables.
• Avoid eating raw shellfish if you have any doubt about its origin or freshness.
• If traveling overseas, make sure your vaccinations are up to date. If you're planning to visit a developing country, visit the travel health website managed by the Centers for Disease Control and Prevention (CDC) to learn which vaccinations are needed before you go. You can also review any information related to water and local food safety.

Summary

Acute diarrhea—the kind that comes on suddenly—is most likely to be contagious. Viral, bacterial, and parasitic causes of diarrhea can be easily spread from person to person.

Children, the elderly, and immunocompromised people are more likely to contract and spread these diarrheal illnesses. They are also more at risk for complications and death.

See a healthcare provider if you fall into any of these groups, if you have diarrhea that doesn't seem to be getting better on its own, or if you have symptoms of dehydration. Your healthcare provider can treat severe diarrhea with medications and fluids.