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How long can a bacterial infection last in your intestines?

Bacterial infections in the intestines, also known as bacterial gastroenteritis, can last anywhere from a few days to a few weeks depending on the type of bacteria causing the infection. Some of the most common bacteria that can cause intestinal infections include Salmonella, Campylobacter, Shigella, E. coli, Clostridium difficile, Yersinia, Vibrio, and Listeria.

What causes bacterial infections in the intestines?

Bacterial infections in the intestines are usually caused by consuming contaminated food or water. The bacteria can also sometimes spread through contact with infected people or animals. The most common ways bacterial intestinal infections spread include:

  • Eating undercooked meat, eggs, or fish contaminated with bacteria
  • Drinking unpasteurized milk or untreated water
  • Eating raw fruits and vegetables contaminated with feces
  • Handling or preparing food without properly washing hands after using the bathroom
  • Eating food prepared by someone with a bacterial infection who did not wash their hands properly
  • Close contact with farm animals or pets who carry intestinal bacteria

Once the bacteria are ingested, they multiply and colonize the intestines, producing toxins that damage the intestinal lining, leading to inflammation, diarrhea, and other gastrointestinal symptoms.

What are the symptoms of bacterial intestinal infections?

Some common symptoms of bacterial infections in the intestines include:

  • Diarrhea – watery, loose stools
  • Cramping and abdominal pain
  • Nausea and vomiting
  • Fever and chills
  • Dehydration
  • Bloody stools (in some cases)
  • Weakness and fatigue

Symptoms can start anywhere from a few hours to a few days after ingesting contaminated food or water. Some types of bacteria also cause more severe symptoms than others.

How long do bacterial intestinal infections typically last?

The duration of intestinal bacterial infections can vary depending on the specific bacterium involved:

Bacteria Typical Duration of Illness
Salmonella 4 – 7 days
Campylobacter 2 – 10 days
Shigella 5 – 7 days
E. coli 5 – 10 days
Clostridium difficile Can relapse and recur
Yersinia 1 – 3 weeks
Vibrio 2 – 5 days
Listeria Short, but can lead to serious complications

As shown, most acute bacterial intestinal infections last anywhere from 2 days to 2 weeks. However, some bacteria like Clostridium difficile and Yersinia can cause more prolonged symptoms lasting several weeks or recurring. Complications can also prolong recovery.

How are bacterial intestinal infections treated?

Most acute bacterial intestinal infections will resolve on their own without antibiotics. Treatment focuses on preventing dehydration from fluid losses by drinking plenty of fluids.

However, some specific treatments may include:

  • Antibiotics – For some severe bacterial infections or those at risk of spreading, antibiotics may be prescribed. These help kill the bacteria faster.
  • Antidiarrheal medications – Medications like loperamide (Imodium) can help slow diarrhea and intestinal cramping.
  • IV fluids – Severe dehydration may require fluids given intravenously in hospital.
  • Probiotics – Can help restore healthy gut bacteria faster after antibiotics.

It’s important to avoid anti-diarrhea medications in general, as they can trap the bacteria in the intestines and prolong symptoms. Most cases will resolve with conservative treatments focused on hydration.

When to see a doctor

You should visit your doctor if you experience any of the following:

  • Diarrhea lasting more than 3 days
  • Bloody or black stools
  • High fever over 102°F (39°C)
  • Signs of dehydration such as dizziness or weakness
  • Inability to keep down fluids due to vomiting
  • Severe abdominal pain or cramps

Seeking medical care promptly can help diagnose the type of bacterial infection through stool testing and allow early treatment of complications.

How to prevent bacterial intestinal infections

You can reduce your risk of bacterial intestinal infections by:

  • Washing hands thoroughly with soap before eating or preparing food.
  • Cooking meats thoroughly to kill any bacteria.
  • Avoiding unpasteurized dairy products.
  • Rinsing fruits and vegetables thoroughly.
  • Avoiding potentially contaminated water sources.
  • Taking antibiotics only when prescribed by a doctor.

Practicing good hygiene and food safety precautions can go a long way in preventing many common bacterial infections. Pay special attention when travelling to places with poor sanitation as well.

When are antibiotics needed for bacterial intestinal infections?

Most cases of intestinal bacterial infections do not require antibiotics for treatment. However, antibiotics may be warranted in some situations such as:

  • Infection with invasive bacteria like Shigella, Campylobacter, or Salmonella Typhi.
  • Infection spreading to the bloodstream (sepsis).
  • Very high fever or severe dehydration.
  • Signs of widespread infection like joint pain.
  • Infection lasting more than 1-2 weeks.
  • Presence of severe abdominal pain, bloody diarrhea, or neurological symptoms.
  • Weakened immune system that makes clearing infection difficult.

Antibiotics used to treat intestinal infections often include ciprofloxacin, azithromycin, or ampicillin. The choice depends on identifying the specific bacterium involved through stool tests. It’s important to complete the full antibiotic course as prescribed to prevent recurrence.

Risks of unnecessary antibiotics

While antibiotics can be lifesaving in bacterial infections, overuse comes with some risks. These include:

  • Antibiotic resistance – bacteria become resistant to drugs, making them ineffective.
  • Recurrence of infection – some bacteria like C. difficile relapse after antibiotics kill off normal gut flora.
  • Side effects like nausea, diarrhea, rashes.
  • Disruption of healthy gut microbiome.

For these reasons, antibiotics should be used judiciously for bacterial intestinal infections when the benefits outweigh potential harms. Mild cases often clear on their own without antibiotics.

How contagious are bacterial intestinal infections?

Bacterial intestinal infections range from mildly to highly contagious depending on the specific bacterium involved. In general:

  • Highly contagious – Shigella, E. coli, norovirus
  • Moderately contagious – Salmonella, Campylobacter, rotavirus
  • Low or limited contagiousness – Clostridium difficile, Yersinia

The bacteria are primarily spread through the fecal-oral route. This includes consuming contaminated food or water or contact with infected feces. Some tips to avoid spreading intestinal bacteria include:

  • Practicing good hand hygiene with thorough hand washing.
  • Avoid preparing food for others while ill.
  • Disinfecting contaminated surfaces and laundering soiled linens.
  • Avoiding pools, play areas, work, or school during illness.
  • Isolating infected household members.

Following prevention guidelines for each specific bacterium can help reduce transmission to others.

Can you get an intestinal infection without symptoms?

It is possible to have an intestinal bacterial infection without developing symptoms, known as being asymptomatic. This is most common with Salmonella and Campylobacter infections.

According to the CDC, it’s estimated that:

  • 1 in 20 Salmonella infections are asymptomatic.
  • Up to 80% of Campylobacter infections may be asymptomatic.

Those at highest risk of asymptomatic infection include:

  • Children under age 5
  • Older adults over 65
  • Those with weakened immune systems
  • People who have had intestinal infections before

Even without symptoms, people can still shed the bacteria in their stool and potentially transmit infection to others. Good hygiene practices are important to reduce this risk of asymptomatic transmission. Stool testing can sometimes detect silent infections.

Risks of asymptomatic bacterial intestinal infections

While asymptomatic bacterial intestinal infections may seem harmless, there are some risks to be aware of:

  • Chronic shedding of bacteria in stool, which can infect others
  • Potential for infection to eventually trigger symptoms
  • Bacteria persisting in gallbladder or other sites, causing relapsing illness
  • In very rare cases, spread of bacteria to the bloodstream (sepsis)

Pregnant women and those with compromised immunity should be especially careful about asymptomatic infections that could lead to complications. Seeking prompt treatment can clear silent infections and reduce risks.

Can intestinal infections lead to long-term complications?

In most healthy individuals, intestinal bacterial infections resolve without long-term complications. However, some potential long-term complications can include:

  • Irritable bowel syndrome – Some research indicates bacterial gastroenteritis increases odds of later developing IBS.
  • Reactive arthritis – Joint pain and inflammation, most often after Campylobacter infection.
  • Guillain-Barre syndrome – Nerve damage causing muscle weakness, usually after Campylobacter.
  • Hemolytic uremic syndrome – Kidney failure, from E. coli Shiga toxin.
  • Post-infectious IBS – IBS symptoms lasting months after acute infection.

Those most at risk of lasting complications include:

  • Young children under age 5
  • Older adults over 65
  • Those with weakened immune systems
  • Individuals with chronic illnesses like diabetes or kidney disease

Seeking prompt treatment for severe intestinal infections can help reduce the likelihood of prolonged complications. Stay alert for persistent symptoms after recovery that may need evaluation.

When are intestinal bacterial infections contagious?

Bacterial intestinal infections are typically most contagious:

  • Shortly before and after symptoms start – Bacteria levels peak during illness.
  • With diarrhea – Shedding of bacteria in watery stool spreads infection.
  • In some cases, while asymptomatic – No symptoms but still infectious.
  • Even after symptoms resolve – Bacteria may still be shed for a short time after.

The exact timeline of contagiousness depends on the type of bacteria. For example:

  • Salmonella: Contagious for up to a week after symptoms end.
  • E. coli: Highly contagious during diarrhea, less so after symptoms stop.
  • Shigella: Very contagious up to 2 weeks after diarrhea ends.
  • Norovirus: Extremely contagious for 2-3 days after recovery.

Practicing good hygiene like handwashing and disinfecting surfaces during this time can help prevent spread. Isolating from work, school, or food handling is also recommended while ill.


Bacterial infections affecting the intestines can be unpleasant and disruptive illnesses. But prompt treatment focused on hydration, rest, and nutrition along with good hygiene practices can help support recovery. Seek medical attention if severe symptoms arise or if illness lasts longer than expected. While most bacterial infections resolve on their own, be alert for potential complications, especially in higher risk groups. Understanding the typical duration of illness and contagious period for specific intestinal bacteria can help manage expectations for recovery and minimize transmission to others.