What are the most common bacterial secondary infections in children after a viral Upper Respiratory Infection (URI)?

Most Common Bacterial Secondary Infections in Children After Viral URI

The three most common bacterial secondary infections following viral upper respiratory infections in children are acute bacterial rhinosinusitis (ABRS) and acute otitis media (AOM), caused predominantly by Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. 1

Primary Bacterial Pathogens

The bacterial organisms that most commonly cause secondary infections after viral URIs are:

• Streptococcus pneumoniae (25-30% of acute bacterial rhinosinusitis cases) 1
• Haemophilus influenzae (15-20% of cases) 1
• Moraxella catarrhalis (15-20% of cases) 1
• Streptococcus pyogenes (2-5% of cases) 1
• Anaerobes (2-5% of cases) 1

Clinical Context: Nasopharyngeal Colonization

Understanding colonization patterns is critical to recognizing why these specific bacteria cause secondary infections:

• By 12 months of age, 70% of children are colonized by at least one of the three major respiratory pathogens (S. pneumoniae, H. influenzae, or M. catarrhalis) 1
• More than 90% of children are colonized with S. pneumoniae by 3 years of age 1
• Colonization with respiratory pathogens increases considerably during winter and during periods of viral URI, which directly leads to bacterial otitis media and sinusitis 1
• During viral URIs, S. pneumoniae recovery from nasopharyngeal cultures increases from approximately 21% in healthy children to 32% during URI episodes 1

Most Common Secondary Infections

1. Acute Bacterial Rhinosinusitis (ABRS)

ABRS complicates approximately 8% of viral URIs in young children 2. The American Academy of Pediatrics defines three specific patterns warranting diagnosis:

• Persistent symptoms: Nasal discharge or daytime cough lasting ≥10 days without improvement (most common presentation, 72% of cases) 1, 3, 2
• Worsening/biphasic course: Initial improvement followed by worsening or new onset of fever, cough, or nasal discharge after 5-7 days 1, 3
• Severe onset: High fever (≥39°C) and purulent nasal discharge for at least 3-4 consecutive days 1, 3

2. Acute Otitis Media (AOM)

AOM is another major bacterial complication, often occurring concurrently with ABRS (32 of 103 ABRS episodes in one study occurred with concurrent AOM) 2. The same three bacterial pathogens (S. pneumoniae, H. influenzae, M. catarrhalis) are responsible 1.

Risk Factors for Bacterial Secondary Infection

Specific factors increase the likelihood of bacterial complications:

• Female sex: Girls have more frequent ABRS episodes than boys (0.5 vs 0.3 episodes/year) 2
• Rhinovirus detection: Positively correlated with ABRS risk 2
• M. catarrhalis colonization: Presence during URI is positively correlated with risk for ABRS 2
• White race: More likely to develop ABRS compared to Black children 2
• Adequate PCV7 vaccination: Paradoxically appeared to increase ABRS risk in one study, likely due to serotype replacement 2

Critical Diagnostic Pitfalls to Avoid

Do not diagnose bacterial infection based on:

• Yellow or green nasal discharge color alone: Mucopurulent secretions commonly occur during uncomplicated viral URIs due to neutrophil influx and represent normal viral illness progression 3, 4
• Duration less than 10 days: Viral URIs commonly last 10+ days, with 7-13% persisting beyond 15 days 4
• Presence of cough and congestion alone: These are the most persistent symptoms in uncomplicated viral infections 4

First-Line Antibiotic Therapy When Indicated

When bacterial infection is confirmed based on the criteria above:

• Amoxicillin with or without clavulanate is first-line therapy for both ABRS and AOM 1
• Consider amoxicillin-clavulanate in cases of severe symptoms, recent antibiotic exposure (<6 weeks), or known high local prevalence of amoxicillin-resistant H. influenzae 1
• Macrolides and oral third-generation cephalosporins are poor choices due to high pneumococcal resistance rates 1

Impact of Pneumococcal Vaccination

The widespread use of pneumococcal conjugate vaccines has altered the epidemiology:

• Decreasing incidence of pneumococcal otitis media and likely ABRS 5
• Evidence of serotype replacement with increases in nonvaccine serotypes, notably serotype 19A (commonly antibiotic-resistant) 1
• Possible increasing prevalence of H. influenzae in these infections 5
• Protective herd immunity effect on adults 5