Paul A. Rufo, MD, MMSc, is an assistant professor of pediatrics and senior investigator in the Center for Inflammatory Bowel Disease at Boston Children's Hospital.
Diarrhea can be caused by many conditions. Some types of diarrhea are contagious and can be spread between people and even from animals to people. Diarrhea can also be a symptom of a disease that is not infectious.
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. They may also be more likely to die from these complications.
This article will go over the types of diarrhea, the causes of diarrhea, how to tell if diarrhea is contagious, and how long infectious diarrhea usually lasts. You will also learn about infectious diarrhea treatments and how to prevent diarrhea.
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 that 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 people don't wash their hands after they use the bathroom, they can spread the infection when they touch other people (for example, by shaking hands). People can also catch infections that cause diarrhea if a sick person makes food for them.
Kids often spread 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 also be transmitted if people don't wash their hands after touching an animal.
Two terms you may here associated with infectious diarrhea:
Infectious diarrhea often comes 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.
Viruses are the most common cause of diarrhea. There are four specific viruses that most often cause infectious diarrhea:
Infectious diarrhea caused by a virus is usually highly contagious.
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. The bacteria that commonly cause infectious diarrheal disease include:
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.
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:
Infectious diarrhea caused by parasites is usually transmitted through infected drinking water.
Infants and young children who go to daycare or preschool are more likely to catch contagious diarrhea illnesses. Things like sharing toys, contact with others in confined spaces, diaper changing/potty training, and inadequate hand washing amongst kids make it easy for germs to spread.
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:
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.
What is considered infectious diarrhea, how long infectious diarrhea will last, and what can be done to treat and prevent this kind of diarrhea depends on the cause.
To find out what that is, you'll need to see 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—for example, if 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:
The treatment for diarrhea depends on the cause and how sick a person is.
For infectious diarrheal diseases, there are medications that can be given. 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. If you have a fever and feel sick when you have diarrhea, an over-the-counter (OTC) fever-reducing or pain-relieving medication may help.
An ounce of prevention is truly worth a pound of cure when it comes to avoiding diarrhea. Here are a few tips for preventing diarrhea infections at home and while you're out:
Diarrhea is often caused by germs. A diarrheal illness that is caused by viruses, bacteria, and parasites is contagious.
Some of the germs that cause infectious diarrhea can be spread through the air, but transmission is more likely when someone vomits.
Some infectious illnesses that cause diarrhea do not always cause a fever. For example, you might not have a fever if you are sick with norovirus ("stomach flu"), which is highly contagious.
Acute diarrhea usually lasts a few days at most. Chronic diarrhea lasts for four weeks or longer. It can also come and go.
How long you can spread infectious diarrhea to other people depends on what is causing it. You might start feeling better but still be able to spread the infection for a few more days.
Your provider can test your stool and see if it has germs—like bacteria or parasites—in it. There are also blood tests that can help your provider see if you have a virus.
Antibiotics are only used when diarrhea is caused by bacteria. Three examples of antibiotics that are used for acute diarrhea are ciprofloxacin, cephalosporin, and azithromycin.
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