What happens if you drink water with bacteria in it?

Drinking water contaminated with bacteria can cause illness. However, the severity of illness depends on the type and amount of bacteria present in the water.

Can you get sick from drinking water with bacteria?

Yes, it is possible to get sick from drinking water that contains harmful bacteria. Bacteria are microscopic organisms that are present virtually everywhere in our environment. Many types are harmless, but some can cause disease.

Water can become contaminated with bacteria from animal or human waste, especially if this waste enters a drinking water source like a well, lake, or stream. Certain bacteria like E. coli, Salmonella, Shigella, and Campylobacter are associated with fecal contamination and can cause illness if ingested.

What types of bacteria are commonly found in contaminated water?

Some of the major types of disease-causing bacteria that may be present in contaminated drinking water include:

  • Escherichia coli (E. coli) – Found in human and animal feces. Most strains are harmless but some can cause diarrhea, urinary tract infections, respiratory illness, pneumonia, and other illnesses.
  • Salmonella – Causes salmonellosis infection with symptoms like diarrhea, fever, and abdominal cramps.
  • Shigella – Causes shigellosis or bacillary dysentery characterized by severe diarrhea with blood and mucus.
  • Vibrio cholerae – Causes cholera, an acute diarrheal illness that can be severe and life-threatening.
  • Campylobacter – A common cause of bacterial gastroenteritis with symptoms like diarrhea, cramping, abdominal pain, and fever.
  • Legionella – Causes Legionnaires’ disease, a serious lung infection.
  • Mycobacterium – Causes tuberculosis and other chronic bacterial infections.
  • Pseudomonas aeruginosa – Can cause a range of infections, especially in people with weakened immune systems.
  • Clostridium botulinum – Causes botulism, a severe paralytic illness from a powerful neurotoxin.

Bacterial contamination can occur if animal or human waste comes into contact with drinking water sources. Proper treatment and disinfection should remove or inactivate harmful bacteria in municipal drinking water. However, untreated water from private wells is at higher risk of bacterial contamination.

What factors determine how sick you can get?

Several key factors influence the likelihood and severity of illness caused by ingesting water contaminated with bacteria:

  • Type of bacteria – Some bacteria like E. coli may cause self-limiting diarrhea while others like Vibrio cholerae can be life-threatening.
  • Number of bacteria (dose) – A higher bacterial load is more likely to make you sick.
  • Your age and health – Young children, older adults, pregnant women, and those with weakened immune systems are more vulnerable to infections from waterborne bacteria.
  • Virulence of the strain – Within a bacterial species, some strains are more pathogenic and dangerous than others.
  • Amount of contaminated water ingested – Drinking a small amount may cause milder illness than drinking a large quantity.
  • Sensitivity of the individual – Each person reacts differently based on factors like their baseline health and gut microbiome.

In healthy adults, a small number of bacteria may cause mild short-term diarrhea. However, a higher dose can lead to severe dehydrating diarrhea requiring medical treatment. At-risk groups like young kids can become extremely ill even with a small number of pathogenic bacteria.

What are the most common symptoms and health effects?

Symptoms commonly associated with drinking water contaminated with bacteria may include:

  • Diarrhea – Can range from mild and temporary to extreme and watery.
  • Abdominal cramps and pain
  • Nausea and vomiting
  • Fever and chills
  • General flu-like symptoms
  • Dehydration – Especially in cases of severe diarrhea.
  • Muscle aches
  • Headaches
  • Bloody stool (in some bacterial infections)

While unpleasant, most cases of diarrhea from bacteria in drinking water are short-lived, lasting around 2-5 days before resolving. However, some bacteria can have more severe effects like:

  • Severe dehydration which can be deadly without fluid replacement
  • Septicemia or bloodstream infection
  • kidney failure or hemorrhagic colitis from powerful shiga toxin-producing bacteria like E. coli O157:H7
  • Guillain-Barre syndrome, a paralytic nervous system disorder caused by Campylobacter
  • Meningitis or encephalitis from bacteria penetrating the central nervous system
  • Reactive arthritis which can become chronic after some gastrointestinal infections
  • Endotoxic shock in susceptible individuals exposed to Gram-negative bacteria like E. coli or Salmonella

Those at highest risk of severe illness or complications include infants, young children, the elderly, pregnant women, and those with compromised immune systems.

How soon after exposure do symptoms appear?

The incubation period before symptoms of bacterial ingestion appear can range from hours to days, depending on the organism:

  • Salmonella – 6 hours to 6 days, commonly 12-36 hours
  • Shigella – 24-48 hours
  • E. coli – 1-10 days, typically 2-5 days
  • Campylobacter – 2-5 days
  • Vibrio cholerae – Few hours to 5 days

In most cases, symptoms will start within 1-7 days after drinking contaminated water. Shorter incubation periods of just a few hours or up to 1-2 days are typically associated with more aggressive pathogens that produce toxins or invasive infections.

Extended incubation periods over 5-10 days are less common but can happen, especially with the bacteria E. coli O157:H7 which has delayed onset but potentially serious complications.

How is the illness diagnosed?

Gastroenteritis or diarrhea from drinking contaminated water is typically diagnosed based on symptoms, medical history, physical examination, and laboratory tests which may include:

  • Stool culture to identify disease-causing bacteria like Salmonella, Shigella, Campylobacter, E. coli.
  • Testing stool for toxins produced by bacteria like C. difficile or E. coli.
  • Microscopic examination of stool for blood, white blood cells, or parasites.
  • Complete blood count (CBC) to check for signs of infection.
  • Electrolyte panel to look for dehydration.
  • Urinalysis if a urinary tract infection is suspected.

In uncomplicated cases, a diagnosis can often be made clinically based on symptoms alone. However, lab tests help confirm the exact type of bacterial infection and guide appropriate treatment.

What is the treatment?

For most cases of waterborne bacterial illness, treatment focuses on:

  • Fluid replacement – Either oral rehydration solutions or IV fluids for severe dehydration.
  • Supportive care – Rest, nutrition, antidiarrheals if needed for moderate symptoms.
  • Antibiotics – Typically not used except for high-risk groups, bloody diarrhea, or known pathogenic strains.

Mild diarrhea often resolves on its own without antibiotics. However, antibiotics can treat certain high-risk scenarios:

  • Infants, children, elderly, or immunocompromised patients.
  • Prolonged symptoms lasting over 1 week.
  • Signs of invasive infection like fever, bloody stool, elevated white blood cell count.
  • Known infection with shiga-toxin producing E. coli which can progress to hemorrhagic colitis, kidney complications.
  • Significant dehydration not improving with fluids alone.

Common antibiotics used for treating bacterial diarrhea include ciprofloxacin, azithromycin, rifaximin, or trimethoprim-sulfamethoxazole. Hospitalization forhydration, monitoring, and treatment may be necessary in severe cases.

How can it be prevented?

Preventing illness from bacteria in drinking water centers around these key strategies:

  • Proper treatment and disinfection of municipal tap and well water supplies.
  • Avoiding cross-contamination between sewage/waste and drinking water sources.
  • Boiling or filtering water from risky sources when traveling in developing regions.
  • Using bottled water when clean tap water is unavailable.
  • Practicing good hygiene and handwashing when handling water containers.
  • Properly disinfecting wells after flooding or contamination events.
  • Testing private well water quality at least yearly.

At home, periodically disinfecting taps, water filters, and fixtures helps reduce bacterial buildup in plumbing systems. Immunocompromised individuals should take extra precautions with water safety, including point-of-use water filters.

What is the outlook for recovery?

The prognosis for recovery from diarrhea due to ingesting bacteria in drinking water is generally very good, especially for healthy adults and older children. Full recovery within 5-7 days would be expected with appropriate rehydration and supportive care.

Patients at highest risk of complications like severe dehydration, septicemia, or kidney problems include:

  • Infants and young children under 5 years old.
  • Elderly adults over 65 years old.
  • Pregnant women – Increased risk to both mother and fetus.
  • Those with weakened immune systems from conditions like HIV/AIDS, cancer treatment, organ transplant, autoimmune disorders.

These vulnerable groups, as well as anyone exhibiting signs of invasive infection, should seek prompt medical attention for hydration, monitoring, and potential antibiotic treatment.

With appropriate care, most people make a full recovery within a week or two after drinking water contaminated with bacteria. However, it highlights the importance of access to clean drinking water free of pathogenic microbes.


Drinking water contaminated with bacteria poses health risks ranging from mild stomach upset to severe life-threatening illness depending on the type and dose of bacteria ingested. Vulnerable groups like young children and the immunocompromised are at highest risk of severe complications and require prompt medical treatment. However, most healthy adults and older children recover fully within a week or two with appropriate rehydration and care. Public health efforts to provide effective water treatment, hygienic practices, and regular testing help prevent outbreaks and limit exposure to waterborne bacterial pathogens.

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