Intestinal infections in children: main causes and treatment

Intestinal infections in children are a group of diseases in which microbes infect the gastrointestinal tract, causing diarrhea, vomiting, abdominal pain, fever, and signs of dehydration. In the vast majority of cases, viruses are the cause, and less commonly, bacteria and protozoa. In most children, the course is acute and self-limiting, but fluid and electrolyte deficiency poses a key threat, especially in children under five years of age. Therefore, the primary task for families and physicians is early assessment of the degree of dehydration and prompt rehydration. [1]

Despite a significant decline in mortality in recent decades, diarrheal diseases remain among the leading causes of death in children under five years of age worldwide. Improved access to clean water, hand hygiene, rotavirus vaccination, and proper use of oral rehydration solutions have dramatically reduced the severity of the disease and hospitalizations. However, the disease burden remains highest in countries with low social development indexes. [2]

From a policy perspective, not every case of diarrhea requires laboratory testing: the diagnosis of acute gastroenteritis is most often clinical. Testing is indicated for severe cases, blood in the stool, high fever, in children at risk, or when an outbreak is suspected. This allows resources to be focused on rehydration, symptom control, and targeted etiotropic therapy where it truly changes the outcome. [3]

It's important for parents to recognize warning signs that require urgent attention: lethargy, intense thirst or refusal to drink, frequent vomiting with inability to keep fluids down, wobbly walking, infrequent urination, sunken eyes, blood in the stool, high fever, or abdominal pain that doesn't subside with bowel movements. Prompt assessment of the severity and proper rehydration reduce the risk of complications. [4]

Code according to ICD-10 and ICD-11

In the International Classification of Diseases, Tenth Revision, intestinal infections are grouped into blocks A00-A09. In practice, codes A08 for viral enteritis, A04 for bacterial intestinal infections, and A09 for infectious gastroenteritis of unspecified origin are often used. When the etiology is established, a specific code is indicated, for example, A08.0 for rotavirus enteritis or A04.7 for enterocolitis caused by Clostridioides difficile. [5]

The International Classification of Diseases, Eleventh Revision, uses the "Gastroenteritis or Colitis of Infectious Origin" block with codes ranging from 1A00 to 1A40. Code 1A22 reflects gastroenteritis caused by rotavirus, and 1A40 is used when the infectious agent is not specified. These codes allow for more accurate documentation of the disease and the comparison of data across countries and healthcare systems. [6]

Table 1. Most commonly used codes

Classifier	Block	Examples of frequently used codes
ICD-10	A00-A09	A08.0 Rotavirus enteritis; A04.7 Enterocolitis due to Clostridioides difficile; A09 Infectious gastroenteritis and colitis, unspecified
ICD-11	1A00-1A40	1A22 Gastroenteritis due to rotavirus; 1A40 Gastroenteritis or colitis, unspecified

Source: ICD-10 and ICD-11 classifiers. [7]

Epidemiology

Diarrheal diseases remain a significant cause of childhood mortality. Global estimates indicate that hundreds of thousands of deaths occur annually in children under five, despite a general downward trend and the success of vaccination and water supply programs. Countries with low human development indexes account for the largest share of losses, measured by disability-adjusted life years. [8]

Rotavirus was and remains a leading cause of severe diarrhea before the introduction of vaccination. Systematic reviews show a significant reduction in hospitalizations after the introduction of rotavirus vaccines, and a global assessment of the impact of vaccination indicates the prevention of a large number of childhood deaths. The higher the immunization coverage, the greater the effect not only in the vaccinated cohort but also at the population level. [9]

Noroviruses are becoming the dominant cause of episodes following mass vaccination against rotavirus, especially in the winter months. Bacterial agents are most often associated with fever and blood in the stool, with seasonal peaks in summer and fall, as well as dietary risk factors and travel. In infants, severity is often determined by dehydration, while in adolescents, it is determined by foodborne illnesses and concomitant diseases. [10]

At the household and childcare level, hand hygiene and safe water practices play a key role. According to a Cochrane review and meta-analyses, handwashing promotion programs reduce the risk of diarrhea episodes by approximately one-third. Infrastructure water and sanitation interventions also demonstrate significant effects. [11]

Reasons

The most common viruses in young children are rotavirus, norovirus, adenovirus, and astrovirus. These agents are transmitted via the fecal-oral route through close contact, contaminated objects, and water. The incubation period is short, and the onset is acute, often accompanied by vomiting, increasing the risk of dehydration. In crowded settings, viruses spread especially quickly. [12]

Among bacterial causes, the most common are Campylobacter, Salmonella, Shigella, infectious Escherichia coli, Yersinia, and, in those hospitalized and receiving antibiotics, Clostridioides difficile. Bacterial diarrhea is typically accompanied by fever, abdominal pain, blood and mucus in the stool, and sometimes severe pain. Foodborne outbreaks are associated with undercooked poultry, eggs, unpasteurized milk, and seafood. [13]

Protozoa such as Giardia and Cryptosporidium are found in children attending daycares and camps, as well as through contact with contaminated water. They often cause persistent diarrhea, weight loss, and lactase deficiency secondary to inflammation. Etiological confirmation is important for therapy selection, as specific antiprotozoal drugs are required. [14]

The role of mixed infections and post-infectious transient malabsorption is also significant. Following viral diarrhea due to damage to the brush border, a temporary deterioration in lactose intolerance is possible, leading to loose stools and flatulence. In such cases, continued breastfeeding and avoiding unnecessary dietary restrictions are helpful. [15]

Risk factors

Ages under five years, especially under two years, are the most significant factors in both the incidence and risk of dehydration due to high fluid requirements and low fluid reserves. Children with malnutrition initially have less compensatory capacity, which increases the likelihood of severe dehydration and hospitalization. [16]

Children's groups, overcrowding, and poor hand hygiene increase the risk of virus transmission. Lack of safe water and sanitation, seasonal outbreaks, and consumption of unsafe food also increase the risk of illness. Travel, contact with animals, and consumption of seafood are associated with certain pathogens, such as vibrios and campylobacter. [17]

Antibiotic use and hospitalization predispose to Clostridioides difficile-associated colitis. Immunosuppression and chronic bowel disease increase the risk of a protracted and complicated course. These factors should be considered when deciding when to expand diagnostic testing and monitoring. [18]

Incomplete rotavirus vaccination increases the risk of severe gastroenteritis and hospitalization in young children. At the population level, high vaccination coverage provides indirect protection even to unvaccinated community members, reducing virus circulation. [19]

Pathogenesis

Viruses and bacteria trigger a cascade of disorders in children: they damage the small intestinal mucosa, disrupt the transport of water and electrolytes, and increase secretions and peristalsis. Many viruses are characterized by enterocytotropism and destruction of villi, leading to the loss of brush border enzymes and osmotic diarrhea. This is why bloating and lactose intolerance are often observed during the recovery period. [20]

Bacteria can cause inflammatory diarrhea through mucosal invasion and toxins. This is accompanied by pain, cramping, and the presence of blood and mucus. Certain toxins stimulate secretion and disrupt the absorption of sodium and water, leading to significant stool volume and the risk of hypovolemia. These mechanisms determine the choice of therapy, including rehydration and antibiotics. [21]

Symptom development depends on the balance of secretion and absorption, the state of motility, and accompanying vomiting. In practice, vomiting interferes with a child's ability to drink and retain oral rehydration solution, so targeted use of antiemetics in the emergency department can improve the success of oral rehydration. [22]

In severe cases, hypovolemic shock and acid-base imbalance develop. Prolonged diarrhea leads to micronutrient deficiencies and nutritional problems. In infants, the relative body surface area, high fluid requirements, and rapid changes in circulating blood volume significantly contribute to the severity of the condition. [23]

Symptoms

The onset is usually acute, with loose stools, vomiting, abdominal pain, and fever. With a viral infection, watery diarrhea and vomiting predominate, while with a bacterial infection, pain, tenesmus, and possible blood in the stool are more common. In infants, symptoms may include refusal to eat, crying without tears, and infrequent urination. [24]

Signs of dehydration are a key indicator of severity. These include lethargy or irritability, dry tongue, sunken eyes, infrequent or absent urine, thirst, and delayed skin fold retraction. When several signs combine, the risk of severe dehydration increases, requiring immediate rehydration. [25]

Foodborne toxic infections are often associated with a specific food or shared meal, with a sudden onset, sometimes accompanied by severe vomiting. With protozoa, symptoms may be less acute but more prolonged, with signs of malabsorption. The presence of blood in the stool and high fever indicates an inflammatory process. [26]

Children with comorbidities often have a more severe course and a slower recovery. In such cases, observation and a low threshold for extensive diagnostics and hospitalization are warranted to prevent rapid progression of dehydration and metabolic disorders. [27]

Classification, forms and stages

Clinically, acute gastroenteritis with watery diarrhea, inflammatory diarrhea with blood, and persistent diarrhea lasting more than two weeks are distinguished. Nosocomial forms and antibiotic-associated diarrhea are considered separately. This classification helps determine indications for testing and etiotropic therapy. [28]

The degree of dehydration is assessed based on clinical signs, categorizing it as no signs, some degree, and severe. This gradation determines the choice of rehydration plan, the route of fluid administration, and the need for hospitalization. In young children, assessment is performed more frequently, as the dynamics can change within hours. [29]

Based on etiology, infections are classified as viral, bacterial, and protozoal. Viral infections are more common in children and are short-lived, while bacterial infections are more often associated with higher fever and blood flow, and protozoal infections are more protracted. Identifying the specific agent influences treatment decisions only in certain cases. [30]

Surveillance systems use codes based on the international classification system, which allow for the consideration of severity, complications, and outcomes. This approach is important for epidemiological surveillance, resource planning, and evaluating the effectiveness of preventive measures, including vaccination and sanitary projects. [31]

Table 2. Clinical assessment of dehydration by signs

Category	Typical signs	Tactics
No signs	Healed skin, normal behavior, normal urinary frequency	Home rehydration solution, observation
Some signs	Thirst, dry mucous membranes, moderately slow return of skin folds	Enhanced oral rehydration under control
Pronounced signs	Lethargy, sunken eyes, refusal to drink, very slow return of skin fold	Emergency rehydration, intravenous route, hospitalization

Source: Clinical guidelines for the assessment of dehydration in children.[32]

Complications and consequences

The main threat is hypovolemic shock with impaired circulation and perfusion of vital organs. In infants, severe dehydration develops quickly with ongoing vomiting and diarrhea, so delaying rehydration is dangerous. In severe cases, intravenous fluids and monitoring are required. [33]

Inflammatory bacterial diarrhea can lead to invasive complications and hemolytic uremic syndrome in infections caused by Shiga toxin-producing Escherichia coli. In such cases, antibacterial therapy without confirmation and control is contraindicated due to the risk of increased toxin production. [34]

Prolonged diarrhea is accompanied by nutritional and micronutrient deficiencies, which impact growth and cognitive development. Nutritional restoration and early return to a normal diet reduce the risk of persistent consequences. Additional correction is necessary if deficiencies are diagnosed. [35]

Post-infectious functional disorders, including transient lactase deficiency, occur after viral gastroenteritis and are usually reversible. Careful expansion of the diet, continued breastfeeding, and the elimination of unnecessary restrictions help to quickly return to normal. [36]

When to see a doctor

Immediately - if you experience lethargy, drowsiness or impaired consciousness, repeated vomiting with the inability to drink, infrequent urination, intense thirst or complete refusal to drink fluids, sunken eyes, cold, marbled skin, blood in the stool, high fever, or severe cramping abdominal pain. These are signs of severe dehydration or a complicated course. [37]

You should seek medical attention immediately if your child is under three months old, has underlying medical conditions, is immunocompromised, has recently been hospitalized, or has taken antibiotics, or if symptoms persist for more than seven days. In these groups, the risk of a protracted and complicated course is higher, and the threshold for advanced diagnostic testing and hospitalization is lower. [38]

It's important to discuss preventative measures with your doctor regularly if your family has a history of frequent episodes of diarrhea, your child attends daycare, or if you haven't been vaccinated against rotavirus. Knowledge of oral rehydration solutions, volumes and frequency of fluid intake, and signs of worsening symptoms are important. [39]

If an outbreak occurs in a group of children or after several people share a meal, a health care provider should be notified. This expedites the epidemiological investigation, targeted diagnostics, and preventative measures, reducing the risk of new cases. [40]

Diagnostics

The diagnosis of acute gastroenteritis in a child is typically clinical and does not require laboratory confirmation. The basis is an assessment of dehydration, frequency and nature of stool, the presence of vomiting and fever, and epidemiological factors. Weight, pulse, respiration, temperature, and urination are measured. In most mild cases, proper oral rehydration is sufficient without testing. [41]

Indications for stool testing include high fever, blood or mucus in the stool, severe abdominal pain and tenderness, signs of sepsis, severe or protracted course, recent hospitalization or antibiotic use, reasonable suspicion of an outbreak, contact with risk factors for vibriosis. In such cases, testing is performed for Salmonella, Shigella, Campylobacter, Escherichia coli, Yersinia, Shiga toxin or gene, and, if appropriate, for Vibrios and Clostridioides difficile. [42]

Molecular panels reduce the time to results and increase sensitivity when indicated, but they are not routinely used for mild cases, as most viral gastroenteritis is self-limiting. Panels are appropriate for severe cases, bloody stools, symptoms lasting longer than seven days, and during outbreaks. The choice of test is coordinated with the local laboratory's capabilities and the epidemiological situation. [43]

Instrumental methods are not required for uncomplicated diarrhea. Ultrasound and other methods are used selectively in cases of suspected intussusception, acute surgical pathology, or severe pain unresponsive to rehydration. Any nutritional deficiencies and iron deficiency anemia are assessed based on clinical indications after the acute phase has subsided. [44]

Table 3. When to send stool for testing

Situation	What to look for
Fever, blood in the stool, severe pain	Salmonella, Shigella, Campylobacter, Escherichia, Yersinia, Shiga toxins
Symptoms lasting more than seven days	Expanded panel of bacterial, viral and parasitic agents
Recent hospitalization or antibiotics	Clostridioides difficile
"Rice" watery stools, seafood, brackish waters	Vibrio
Suspected outbreak	Dashboard for the epidemiological situation, data exchange with the epidemiological service

Source: Clinical practice guidelines for infectious diarrhea. [45]

Differential diagnosis

Infectious diarrhea should be distinguished from surgical causes of abdominal pain, such as intussusception, appendicitis, and intestinal torsion. Severe localized tenderness, persistent unilateral pain, vomiting with greenish stool, and stool and gas retention require urgent surgical evaluation. Infectious diarrhea is usually accompanied by repeated bowel movements and pain relief after defecation. [46]

Functional diarrhea and irritable bowel syndrome in adolescents rarely present acutely with high fever or blood in the stool. The presence of these symptoms and a severe systemic reaction is more consistent with infection. Post-infectious lactase deficiency manifests as bloating, watery stools, and rumbling associated with dairy products during the recovery period. [47]

In infancy, it's important to be aware of food allergies with a colitis-like presentation. These produce mucus and blood streaks without high fever or systemic intoxication, and diagnosis is based on exclusion and progression with an elimination diet. If in doubt, an in-person pediatric evaluation is required. [48]

Finally, gastrointestinal manifestations of systemic infections and sepsis can masquerade as "common" gastroenteritis. Lethargy, mottled skin, cold hands and feet, and prolonged capillary refill time are all signs that require immediate hospitalization and fluid therapy. [49]

Treatment

The mainstay of treatment is rehydration. In the absence of signs of severe dehydration, oral rehydration solutions with the correct glucose-to-sodium ratio are used. Give small amounts frequently, based on age and weight, replenishing losses after each loose bowel movement and episode of vomiting. Early feeding accelerates mucosal recovery and reduces the duration of diarrhea. [50]

For vomiting in emergency departments, a single dose of an antiemetic is indicated to enhance the success of oral rehydration. Studies show that a single dose of ondansetron improves fluid retention and reduces the need for intravenous therapy in children with dehydration. Regular repeat doses are not prescribed without clinical justification. [51]

Zinc supplementation in children under five years of age reduces the duration of bowel movements and stool volume. The World Health Organization and the United Nations Children's Fund recommend giving ten milligrams per day to children under six months and twenty milligrams per day to older children for fourteen days. This effect has been replicated in modern reviews. [52]

Diosmectite-based sorbents can reduce stool volume and symptom duration in children with mild to moderate dehydration. The safety profile is favorable, but the quality of evidence varies, so the drug is considered an adjunct to rehydration therapy. It is not used as a substitute for rehydration therapy in cases of severe dehydration. [53]

The antisecretory drug racecadotril has been shown in studies to reduce stool volume and the need for infusions during acute diarrhea in children, facilitating home management. It is used as an adjunct to oral rehydration solutions in outpatient settings in the absence of signs of invasive diarrhea. The decision to prescribe is based on age, weight, and local protocols. [54]

Probiotics are considered on a targeted basis and only for specific strains, as their effectiveness varies. Current positions of European probiotic societies clarify which strains are not recommended due to lack of effectiveness and emphasize that the role of probiotics is complementary to rehydration. The choice of strain and duration is based on updated guidelines. [55]

Antimotility drugs are not recommended for children with acute infections due to the risk of complications and masking a severe course. In particular, loperamide-based drugs are contraindicated in infants and are not recommended according to guidelines for infectious diarrhea in pediatrics. This prohibition is especially important in cases of blood in the stool and fever. [56]

Antibacterial therapy is indicated selectively for shigellosis, cholera, severe campylobacteriosis diarrhea, typhoid-paratyphoid infections, generalized forms, and in infants and immunocompromised patients, as indicated. If infection with Shiga toxin-producing Escherichia coli is suspected, antibiotics are contraindicated until this pathogen is excluded. The choice of drug and duration are determined by age, severity, and local resistance data. [57]

In cases of severe dehydration or failure of oral rehydration, intravenous fluids are indicated, with monitoring of vital signs and electrolytes. Management includes assessment of acid-base balance and correction of potassium and sodium imbalances. After stabilization, early return to oral rehydration and nutrition is essential. [58]

Table 4. Choice of treatment tactics

Scenario	What to do now	What else should we discuss?
Mild acute gastroenteritis without dehydration	Oral rehydration solution, early feeding	Sorbent diosmectite as an auxiliary agent
Vomiting interferes with drinking	Single-dose ondansetron in the emergency department	Tests and hospitalization if oral rehydration therapy fails
A child under five years of age	Zinc ten or twenty milligrams per day for fourteen days	Controlling nutrition, returning to a normal diet
Blood in the stool, high fever	Stool for bacterial pathogens and Shiga toxin	Targeted antibacterial therapy according to indications
Signs of severe dehydration	Intravenous rehydration, monitoring	Transfer to oral rehydration upon stabilization

Source: international recommendations. [59]

Table 5. Antibacterial therapy: when appropriate

The alleged agent or situation	Approach
Shigella	Antibacterial therapy according to local sensitivity, short course
Campylobacter in severe cases	Macrolide according to indications
Cholera	A short course of antibiotics plus aggressive rehydration
Typhoid-paratyphoid infections and invasive forms	Antibacterial therapy according to standards
Suspected Shiga toxin-producing Escherichia coli	Antibiotics are contraindicated until this pathogen is excluded.

Source: Infectious diarrhea guidelines. [60]

Prevention

Rotavirus vaccination significantly reduces the risk of severe diarrhea and hospitalization in infants and provides indirect population protection at high coverage. High-coverage programs prevent tens of thousands of hospitalizations and a significant number of deaths, making vaccination one of the most effective prevention tools. [61]

Handwashing with soap at key times—after using the toilet, before preparing and eating food, and after changing diapers—reduces the risk of diarrhea by approximately one-third. Cochrane reviews confirm the effectiveness of handwashing promotion programs. These measures are especially important in childcare settings and families with young children. [62]

Safe water, proper food storage and preparation, pasteurization of milk, and adequate cooking of meat and eggs prevent foodborne outbreaks. Caution is especially emphasized with seafood and water from open water bodies, which may be associated with vibrios. [63]

Parent education programs about oral rehydration solutions, signs of dehydration, and warning signs reduce hospitalizations and improve outcomes. Accessible sachets and clear instructions for preparation are essential parts of a home medicine cabinet for families with young children. [64]

Table 6. Five steps of prevention

Step	What to do
Vaccination	Complete the rotavirus course according to the national calendar
Hand hygiene	Washing hands with soap at key times for the whole family
Safe water	Use safe sources and store water properly
Food	Cook meat and eggs only, and avoid unpasteurized milk and risky seafood.
Education	Keep oral rehydration solution at home and know the signs of dehydration

Source: International Prevention Reviews. [65]

Forecast

Most children have a favorable prognosis, especially with early oral rehydration and continued nutrition. Viral gastroenteritis usually resolves within a few days, and the recovery period is characterized by a rapid return of activity and appetite. The key to success is preventing severe dehydration. [66]

At the population level, the introduction of rotavirus vaccination and hand hygiene programs reduces hospitalizations and deaths. This changes the pattern of etiologies, shifting the focus toward noroviruses and certain bacterial pathogens, requiring the maintenance of surveillance and outbreak preparedness. [67]

A poor prognosis is associated with severe dehydration, young age, malnutrition, comorbidities, and delayed seeking of medical care. In these groups, the threshold for hospitalization and advanced diagnostics should be lower. [68]

With proper family information and access to oral rehydration solutions, most episodes can be managed at home with observation. Further measures include relapse prevention and age-appropriate vaccination. [69]

FAQ

How can you tell if your child is dehydrated and needs medical attention?
Look for lethargy, infrequent or absent urine, a dry tongue, sunken eyes, thirst or refusal to drink, and very slow skin fold retraction. A combination of these signs requires immediate medical attention, especially in young children. [70]

Should a stool sample be tested for every episode of diarrhea?
No, with a typical mild case, testing is not required. Testing is indicated for blood in the stool, high fever, severe pain, prolonged illness, after hospitalization or while taking antibiotics, and if an outbreak is suspected. [71]

Can children be given medications that reduce peristalsis?
No, such medications are not recommended for children due to the risk of complications and masking a severe condition. Exceptions include certain non-infectious situations, as prescribed by a specialist. [72]

Do probiotics help?
Their role is supportive and depends on the specific strain. Current societal positions clarify which strains are not recommended due to lack of effectiveness. Rehydration and nutrition remain the mainstay. [73]

Why is zinc needed?
Zinc reduces the duration and severity of diarrhea in children under five years of age. The recommended dose is ten or twenty milligrams per day for fourteen days, depending on age. [74]

When are antibiotics warranted?
Only for certain bacterial infections and clinical scenarios. If Shiga toxin-producing Escherichia coli is suspected, antibiotics are contraindicated until the pathogen is excluded. [75]

Is it worth giving an antiemetic?
In emergency departments, a single dose of ondansetron helps maintain oral rehydration solution and reduce the need for intravenous therapy. This is used short-term and as indicated. [76]

Can I continue breastfeeding and formula?
Yes, continuing to breastfeed will speed up recovery. There's no need to routinely eliminate dairy products unless you have an individual intolerance.