By Santa J. Bartholomew M.D. FAAP, FCCM
Respiratory Syncytial Virus (RSV) is a single stranded RNA virus that attacks the respiratory system in people of all ages but is particularly dangerous in the very old and very young. It typically causes seasonal outbreaks of disease from October to April. In the past year with COVID precautions (mask wearing, school closures and physical distancing) there were marked reductions in other respiratory viruses including RSV. RSV is the most common virus causing lower respiratory tract disease (pneumonia) in children under 12 months of age.
Hospitalization rates are 4.4/1000 children and are highest in the under 6-month-old population (20/1000 children). Although severe RSV disease is seen mostly in younger infants it can also be seen in the neurologically debilitated and in immunocompromised children in its severest forms.
RSV is an important cause of death in infants and young children estimated at 2.3% mortality in neonates, 6.7% in infants up to a year old. It has been estimated to have caused more deaths in infants and children worldwide than any other infectious agent except for malaria. In the USA mortality rates are estimated at 3.1/100,000 person years in children under a year of age.
RSV has been estimated to have caused more deaths in infants and children worldwide than any other infectious agent except for malaria.
Risk Factors for Getting RSV
- Infant less than 6 months old born in RSV season
- Infants attending daycare or who have older siblings attending daycare
- Infants with lung disease like BPD (bronchopulmonary dysplasia)or cystic fibrosis.
- Infants born < 35 weeks gestation
- Infants and children with congenital heart disease
- Infants exposed to secondhand smoke.
- HIV exposed, uninfected infants
- Children with trisomy 21 (Down’s syndrome)
- Children that are immunocompromised (SCID, cancers, transplant patients)
- Children with persistent asthma
- Children under 5 years old who are socially vulnerable (young maternal age, no heat or running water in home, no electric in home, parents with psychiatric disease)
Transmission & Incubation
- RSV is typically transmitted by direct contact. It can survive for several hours on hands, toys and other surfaces. So if those become the repository for mucous infected with RSV it is easy to pass to another child via sharing of utensils, bottles, pacifiers, toys or simply touching these infected items.
- Most infected people shed virus for 11 days however young infants can she for up to 4-6 weeks.
- The virus incubates in its new host for 4-6 days before causing signs or symptoms of disease.
- By 2 years of age virtually all individuals have been infected with RSV but unfortunately that does not prevent reinfections or provide substantial immunity.
Pathogenesis
- After exposure the virus reproduces (replicates) in the nose and throat in the small bronchiolar epithelial cells.
- It spreads via secretions to the lower lung and by 1-3 days after exposure can begin to cause lower lung symptoms: cough, increased breathing rate, struggling with breathing.
- It causes a vigorous immune response which can cause further debris in the airways along with bronchoconstriction and this can lead to wheezing that is typically unresponsive to therapy with beta-agonists like Albuterol.
- RSV is highly restricted to the lung. It only very rarely causes disease outside the lung. These extrapulmonary places are typically: liver, spinal fluid and pericardial fluid.
Clinical Features
- Fast breathing
- Bronchospasm
- Poor feeding
- Fever
- Runny nose, congestion and cough
- Some children with severe disease present with abnormal electrolytes specifically sodium.
- APNEA in infants is not uncommon
Diagnosis & Treatment
CLINICAL SUSPICION
There are now PCR based tests for RSV as well as many other viruses that cause disease in children. These are most helpful in advising families about the course of disease as to date there are no treatments for RSV or most other winter viruses.
DIFFERENTIAL DIAGNOSIS
- Other winter viruses: human metapneumovirus, adenovirus, rhino/enterovirus
- Bacterial pneumonia
- Wheezing without infection
TREATMENT
Supportive (Suctioning, IVF if child cannot eat, Oxygen)
Prognosis
Disease if often self-limited and mortality in USA is low (0.1% in infants), mortality is higher in low-birth-weight premature infants and those with underlying heart disease or pre-existing pulmonary disease. Deaths in these circumstances are often caused by complications of disease such as bacterial superinfections with respiratory failure and not the primary viral disease.
Thirty percent of infants previously diagnosed with RSV will have wheezing beyond the course of their disease that can last many months. Some infants have experienced prolonged loss of voice or hoarseness of voice, difficulty feeding.
Overall, most infants and children recover and go on to live healthy normal lives.
