What are the signs and symptoms of Respiratory Syncytial Virus (RSV) infection, especially in high-risk populations such as infants under two years of age, older adults, and individuals with weakened immune systems or underlying health conditions like heart disease or lung disease?

RSV Signs and Symptoms

RSV infection presents with a spectrum of symptoms ranging from mild upper respiratory tract illness to severe lower respiratory tract disease, with initial symptoms including nasal congestion, rhinorrhea, cough, and fever, progressing to wheezing, rapid breathing, and respiratory distress in more severe cases. 1

Clinical Presentation by Disease Severity

Upper Respiratory Tract Symptoms (Initial Phase)

The infection typically begins with 2-4 days of upper respiratory symptoms before potential progression to lower respiratory tract involvement 2:

• Nasal congestion and rhinorrhea (clear, watery discharge initially) - the hallmark early presentation 1, 2
• Sneezing 2
• Cough - reported in ≥40% of children across studies 3
• Fever - common but not universal 1, 3

Lower Respiratory Tract Symptoms (Progressive Phase)

When infection progresses beyond the upper airways, patients develop 1:

• Wheezing 1
• Rapid breathing (tachypnea) 1
• Difficulty breathing/shortness of breath (dyspnea) - reported in ≥40% of cases 1, 3
• Abnormal breath sounds 1
• Increased work of breathing including nasal flaring and intercostal retractions 2
• Sputum production (particularly in adults) 3

Severe Manifestations

In high-risk populations, severe complications can occur 1:

• Respiratory failure 1
• Apnea (particularly in young infants) 1, 2
• Brief resolved unexplained events (BRUEs) 1
• Lethargy 1
• Feeding abnormalities - reported in ≥40% of children 3

Age-Specific Symptom Patterns

Infants and Young Children (≤5 years)

Approximately 90% of children are infected within the first 2 years of life, with the most severe disease occurring in those under 12 weeks 2:

• Prominent rhinorrhea followed by lower respiratory symptoms is the typical progression 2
• Feeding difficulties are particularly common in infants 3
• Apnea is more frequent in very young infants (<12 weeks) 1, 2
• Infants 1-12 months are more likely to progress rapidly from rhinorrhea to increased work of breathing 2

Older Adults (≥60 years)

Adults present with more severe lower respiratory symptoms and higher risk of complications 1:

• Cough, sputum, dyspnea, and fever/feverishness reported in ≥40% of cases 3
• Higher risk of pneumonia 1
• Exacerbation of underlying chronic conditions (heart disease, COPD, diabetes) 1

Immunocompromised Patients

This population experiences distinct disease characteristics 1:

• More prolonged viral shedding 1
• Higher risk of progression from upper to lower respiratory tract disease 1
• Increased risk of severe disease and mortality 1
• Profound lymphopenia (<100 cells/mm³) is associated with progression to lower respiratory tract disease 4

Symptom Duration and Clinical Course

Timeline

• Initial upper respiratory phase: 2-4 days 2
• Symptoms can last for weeks and vary by geography 3
• Peak incidence: December through March in North America, though regional variations exist 2

Hospitalization Duration

Hospital length of stay varies significantly by age and geography 3:

• Children: Median 2 days (United States) to 7.5 days (China) 3
• Adults: Median 6-15 days across studies 3
• Children <1 year with Down syndrome: Median 4 days 4

Diagnostic Considerations

Clinical Recognition Challenges

RSV symptoms are indistinguishable from other viral respiratory infections, especially in neonates 1:

• Other viral causes include rhinoviruses, parainfluenza, influenza, adenoviruses, and human metapneumovirus 2
• During RSV season (November-March), assume RSV when an infant <1 year presents with rhinorrhea 2
• Laboratory confirmation is required for definitive diagnosis 1

Testing Modalities

• Rapid antigen detection tests have variable sensitivity 1
• Molecular diagnostic tests (RT-PCR) are more sensitive and preferred 1
• Testing is particularly important in high-risk populations for risk stratification 5

High-Risk Features Predicting Severe Disease

Patient Characteristics

The following factors increase risk of severe RSV disease 1, 6:

• Age extremes: <6 months (especially <12 weeks) and ≥60 years 1, 2
• Prematurity: Especially ≤35 weeks gestation 2, 6
• Chronic lung disease (bronchopulmonary dysplasia requiring oxygen, bronchodilators, diuretics, or corticosteroids) 2, 6
• Hemodynamically significant congenital heart disease 2, 6
• Immunocompromised status 1, 6
• Neuromuscular disorders impairing secretion clearance 2, 6
• Down syndrome 4, 6

Environmental and Social Factors

Additional risk factors include 6:

• Multiple birth, male sex
• Low socioeconomic status
• Crowded living conditions, young siblings
• Maternal smoking and indoor smoke pollution
• Day care attendance
• Lack of breastfeeding

Critical Pitfalls to Avoid

• Do not assume mild upper respiratory symptoms will remain mild in high-risk infants—monitor closely for progression to lower respiratory tract disease 2
• Do not dismiss RSV in older children and adults—almost half of RSV hospitalizations occur in children >6 months, and adults can develop severe disease 7
• Do not overlook feeding difficulties in infants as an early sign of respiratory compromise 3
• Do not confuse RSV symptoms with other viral illnesses without testing in high-risk populations where specific management may be indicated 1