What are the most common infections in children?

Most Common Infections in Children

Upper respiratory tract infections are the most common infections in children, followed by lower respiratory tract infections, urinary tract infections, and skin/soft tissue infections, with specific pathogens varying by age group and infection site.

Respiratory Tract Infections

Upper Respiratory Tract Infections

• Upper respiratory tract infections (URTIs) are the most frequently encountered infections in children, accounting for the majority of outpatient visits 1
• Common URTIs include acute otitis media, sinusitis, and pharyngitis 1
• It is estimated that 10-15% of children experience recurrent respiratory tract infections 2
• The most commonly accepted definition for recurrent respiratory infections is eight or more documented episodes per year in preschool children (up to three years old) and six or more in children older than three years 2

Lower Respiratory Tract Infections

• Bronchiolitis is a common lower respiratory tract infection affecting infants and children younger than 2 years 3
• Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis in young children 3
• In pneumonia cases, viruses are most commonly found as causative agents in younger children 4
• Streptococcus pneumoniae is the most common bacterial cause of pneumonia in childhood across all age groups 4
• In older children with pneumonia, when a bacterial cause is found, it is most commonly S. pneumoniae followed by Mycoplasma pneumoniae and Chlamydia pneumoniae 4
• A significant proportion (8-40%) of community-acquired pneumonia cases in children represent mixed viral-bacterial infections 4

Urinary Tract Infections

• Urinary tract infections (UTIs) are an important cause of fever in young children 4
• The prevalence of UTIs in young children aged 2 months to 2 years with no identifiable source for fever is approximately 3-7% 4
• UTI prevalence rates vary by age and gender:
  • Girls younger than 1 year: 6.5% 4
  • Girls aged 1-2 years: 8.1% 4
  • Boys younger than 1 year: 3.3% (circumcised: 1.2%, uncircumcised: 8%) 4
  • Boys aged 1-2 years: 1.9% 4
• Children with higher fevers (≥39°C/102.2°F) may have a higher prevalence of UTI 4

Skin and Soft Tissue Infections

• Bacterial skin infections represent a significant health burden in children 5
• Common skin infections include:
  • Impetigo: a common, self-limited infection caused by Staphylococcus aureus (bullous form) or beta-hemolytic streptococci, S. aureus, or both (non-bullous form) 5
  • Folliculitis: infection of hair follicles mostly caused by S. aureus 5
  • Cellulitis and erysipelas: rapidly spreading, painful superficial skin infections, usually caused by streptococci or S. aureus 5
  • Abscesses: collections of purulence in the dermis and deeper tissues caused by S. aureus or polymicrobial infections 5

Age-Related Patterns of Infection

• Infants and Toddlers (0-2 years):

  • Viral infections predominate, especially respiratory syncytial virus 4, 3
  • Bacterial pneumonia is less prevalent, but when present, S. pneumoniae is the most common pathogen 4
  • Uncircumcised male infants have higher rates of UTIs compared to circumcised males 4

• School-aged Children and Adolescents:

  • Bacterial infections become more common 4
  • M. pneumoniae and C. pneumoniae infections increase in prevalence 4
  • S. pneumoniae remains the most common bacterial cause of pneumonia 4

Hospital-Acquired Infections in Children

• The most frequent hospital-acquired infections in children involve the urinary tract, respiratory tract, skin, wounds, and gastrointestinal tract 6
• Common causative agents include Staphylococcus aureus, E. coli, Klebsiella, Enterobacter, Pseudomonas, Proteus, fungi, and viruses 6

Special Considerations

• Children with delayed neurodevelopment are at higher risk for aspiration-related lung infections, often involving anaerobic organisms and Streptococcus milleri 4
• Foreign body aspiration can lead to lung infections, typically involving anaerobes and Streptococcus milleri 4
• In developing countries, the bacterial profile differs with S. aureus being the predominant pathogen in respiratory infections, especially during hot and humid months 4