Contagious Diarrhea: Causes, Treatments, and More

Acute diarrhea, or the kind that comes on quickly and lasts up to a few days, is usually contagious. Common causes of contagious diarrhea include viruses, bacteria, and parasites.

Diarrhea is characterized by loose bowel movements three or more times in one day. It can be chronic (long-term) or acute. Diarrhea of any kind has a wide range of causes. Certain medications, food intolerance, and diseases may cause chronic, non-infectious diarrhea.

Viruses, bacteria, or parasites cause contagious diarrhea. These germs spread via fecal-oral transmission. They are shed in the stool of one person and somehow enter the mouth of the next.

Viruses

Viruses are the most common cause of diarrhea that’s passed between people. A person can spread a virus if they do not wash their hands after using the bathroom and then handle food or touch a surface.

The most common viruses that can cause diarrhea include:

• Influenza
• Rotavirus (in children)
• Norovirus

Norovirus, in particular, often causes contagious diarrhea. It typically spreads on cruise ships or other situations in which people live in close quarters.

Bacteria

Many types of bacteria that cause diarrhea stem from contaminated food. It’s also possible for people infected with the bacteria to spread it to others.

The most common types of bacteria that can cause diarrhea include:

• Campylobacter
• Escherichia coli (E. coli)
• Salmonella
• Shigella

Parasites

Parasitic infections are less common than viral infections. Parasites that can cause diarrhea include:

• Cryptosporidium enteritis
• Entamoeba histolytica
• Giardia lamblia

Not all instances of diarrhea are contagious. Chronic diarrhea is typically a side effect of medications or a sign of underlying diseases like:

The biggest indicator that diarrhea is contagious is that it comes on quickly. “Things like that can clue you in—it comes on all of a sudden, you’ve been around someone sick, recently traveled, or ate spoiled food,” Carolyn Newberry, MD, a gastroenterologist at Weill Cornell Medicine, told Health.

An acute case of diarrhea is something that “happens like once a year for most people,” Lisa Ganjhu, DO, a gastroenterologist at NYU Langone, told Health. It’s so infrequent, and most of us know how to deal with it, so infectious diarrhea usually doesn’t get diagnosed.

A healthcare provider can tell whether viruses, bacteria, or parasites are causing diarrhea with a simple stool test. “There are a lot of different bugs we can actually test for,” said Dr. Ganjhu.

You might not have known it, but you have likely had contagious diarrhea before and already know how to treat it. “If you have a healthy immune system, you’ll be sick for a few days, and it will clear up on its own,” said Dr. Newberry. 

Stick to foods that are gentle on your stomach. Make sure you drink a lot of water and something with minerals, like sports drinks or enhanced waters, to replenish electrolytes. You can also use an over-the-counter (OTC) medication like Pepto Bismol (bismuth subsalicylate) to calm your stomach. 

You can do the following to protect yourself and others from contagious diarrhea:

• Avoid touching commonly used surfaces
• Keep your distance if you are sick
• Sanitize or disinfect surfaces if you share a space with someone who’s sick
• Wash your hands with soap and water regularly

Bacteria and parasites are also often found in contaminated food and water. Make sure to cook poultry, meat, or shellfish all the way through before eating. Abide by other food-safety practices, like keeping perishable items refrigerated and properly washing all fruits and vegetables.

The water consumed in the United States will most often be safe. There can still be danger in areas with poor sewer systems or after flooding or heavy storms, which can wash sewage into drinking water. Your city will likely send out a water boil alert. You may be instructed to not only boil tap water but use bottled water to avoid illness.

Diarrhea is one of the most contagious illnesses. Causes of contagious diarrhea include viruses, bacteria, and parasites. This type of bacteria is typically short-lasting and goes away with plenty of hydration and rest.

You will ultimately want to keep in mind how easily infectious diarrhea spreads from person to person to avoid it. Make sure to stay away from others if you or they are sick, and wash your hands regularly.