Respiratory syncytial virus infection

Disease Description (Causes and Symptoms)

• Definition: A respiratory infection caused by infection with respiratory syncytial virus (RSV). It is so common that nearly all children become infected at least once by age 2. Adults usually have mild cold-like symptoms, but severe disease can develop in infants and young children, older adults, and immunocompromised people.
• Pathophysiology: Infection of epithelial cells in the upper respiratory tract → formation of syncytia (syncytium) through cell fusion, increased airway inflammation and mucus production → bronchiolar obstruction and impaired airflow → wheezing, hypoxemia, and other symptoms.
• Main cause: RSV (transmitted through direct contact, droplets, or contaminated objects). Incubation period: 2–8 days.
• Typical symptoms: Cough, runny nose, nasal congestion, fever, sputum, tachypnea (difficulty breathing), wheezing, reduced feeding and fluid intake, and, in severe cases, cyanosis (hypoxia).

Treatment Methods and Precautions

• Basic principles: Mostly conservative (symptomatic) treatment — fluid intake, fever reduction, nasal suction (for infants and young children), and oxygen therapy when there is difficulty breathing.
• Medications/Procedures
  • Antiviral medication: Inhaled ribavirin is used restrictively and selectively in severe or high-risk groups (e.g., very premature infants, people with severe underlying disease, and immunocompromised people). Its use, benefits, and side effects should be carefully evaluated.
  • Antibiotics: Used only when a concurrent bacterial infection is suspected.
  • In severe cases: Intensive care, such as mechanical ventilation or endotracheal intubation, may be required.
• Prevention (high-risk groups)
  • Palivizumab: Monthly intramuscular injections during the RSV epidemic period (e.g., September to March according to RAG criteria) are given to high-risk infants and young children (including premature infants and those with chronic lung disease or congenital heart disease) to prevent severe disease. There are also cases in which RSV immunoglobulin (IV or IM) is used.
  • Vaccines: Preventive vaccines traditionally used widely for infants and young children are limited, but vaccine development and approval for adults and pregnant women have recently occurred, so prevention strategies are changing (recommendations for direct vaccination of infants and antibody policies differ by target group).
• Lifestyle management and precautions
  • At home: Ensure adequate fluid intake and manage fever, relieve nasal congestion (nasal irrigation and suction), and minimize contact with others (especially to protect infants, young children, and older adults).
  • When to visit a hospital: Difficulty breathing (tachypnea, chest retractions, or persistent wheezing), low oxygen saturation (e.g., below 92%; this may vary depending on the clinical situation), a rapid decrease in intake or dehydration, persistent high fever, and other such symptoms.
• Complications
  • Bronchiolitis, pneumonia, worsening of bronchopulmonary dysplasia, and severe respiratory failure. In the long term, an association with asthma and abnormal pulmonary function has been reported (increased among patients hospitalized with severe disease).
• Prognosis
  • Most people recover, but hospitalization and mortality rates are higher among infants and high-risk groups (RAG: mortality rate of approximately 2% when hospitalized for lower respiratory tract infection). The hospitalization rate is high when infection occurs within the first 3 months of life.

Checklist Before an Outpatient Visit (Including Suggested Items to Bring and Questions)

• Items to bring (recommended)
  • List of currently used medications (including dosage and administration times)
  • Medical history: Whether the child was born prematurely; presence of chronic lung disease, congenital heart disease, or immunodeficiency; previous hospitalizations and history of respiratory disease
  • Date recent symptoms began (including the start date of fever and cough), temperature records, intake (breast milk, formula, and food), and urination and bowel movement patterns
  • If possible, home oxygen saturation (pulse oximeter) readings
  • History of exposure to infection at childcare facilities or at home (whether household members have symptoms)
  • Copies of previous test results (chest X-ray, blood tests, and viral tests)
• Items useful to record during the outpatient visit
  • Respiratory rate (per minute), frequency of wheezing and coughing, lethargy or reduced feeding, and presence or absence of cyanosis
• Photos/videos to submit to the doctor before the visit
  • Photos/videos of the child while feeding and of chest retractions (indrawing) or nasal flaring during difficulty breathing

Examples of General Questions to Ask the Doctor

• What is the purpose of this medication (or treatment), and what side effects can be expected?
• When should we be reevaluated (return for a follow-up visit)? What signs mean that we should go to the emergency room?
• How likely is hospitalization to be necessary? What are the criteria for needing oxygen therapy?
• What measures can I take at home to prevent infection?

Examples of Disease-Specific Questions

• (For caregivers of high-risk infants and young children, such as premature infants or children with congenital heart disease) Is my child eligible for palivizumab (once a month)? How are the timing and duration of administration determined?
• What measures can be taken to reduce the risk of asthma (or recurrent wheezing) after my child has been infected with RSV?

(Summary for Reference)

• Typical incubation period: 2–8 days, with a tendency toward seasonal epidemics (autumn to early spring). Severe disease and hospitalization rates are higher in high-risk groups. Treatment is mainly supportive, while ribavirin, hospitalization, and palivizumab prophylaxis may be considered for high-risk and severely ill patients.