What is RSV?
RSV stands for respiratory syncytial virus. It is a common respiratory virus that usually causes mild, cold-like symptoms. RSV is the most common cause of bronchiolitis and pneumonia in children under 1 year of age in the United States.
Who is affected by RSV?
Almost all children get an RSV infection by their second birthday. RSV infections are most likely to become severe in:
- Premature infants
- Newborns up to 6 months of age
- Infants with chronic lung disease or congenital heart disease
- Infants with weakened immune systems
RSV can affect adults too but typically only causes mild symptoms like a cold. However, RSV can be more dangerous for older adults, especially those over age 65 with heart and lung diseases or a weakened immune system.
When does RSV spread?
RSV is highly contagious and spreads mostly during fall, winter, and spring in temperate climates like the United States. Outbreaks of RSV happen annually, often starting in late fall and peaking in late winter.
The RSV season may last from November to March or April, but the exact timing can vary. Warmer climates may experience RSV outbreaks year-round.
How does RSV infection start?
RSV spreads when an infected person coughs or sneezes near you and you breathe in droplets containing the virus. It can also spread by touching contaminated surfaces and then touching your nose, mouth or eyes before handwashing.
It typically takes 2 to 8 days from the time of infection until RSV symptoms first appear, with an average of 4 to 6 days. This incubation period is when the RSV virus is multiplying and spreading in the respiratory system but symptoms are not yet apparent.
Early symptoms of RSV
Early symptoms of RSV often resemble a common cold. The earliest signs may include:
- Runny nose
- Decreased appetite
- Cough
- Sneezing
- Fever
Fever is common during an RSV infection, with temperatures often reaching 100-102°F. Cough tends to become more prominent after a few days.
How does RSV progress?
In mild cases, RSV runs its course over 7 to 10 days. But in young infants or people with weakened immune systems, RSV can quickly progress from upper respiratory symptoms to lower respiratory infection and breathing problems.
Progression of RSV symptoms
As RSV progresses beyond the initial cold-like symptoms, signs may include:
- Worsening cough
- High fever above 102°F
- Wheezing, gasping, or trouble breathing
- Ear infections or sinus infection
- Decreased activity and lethargy
Progression to lower respiratory infection is more likely in infants under 6 months and those born prematurely. Call the doctor if an infant has fever, wheezing, rapid breathing, or blue-tinged skin which may signal oxygen deprivation.
Bronchiolitis
Many severe RSV infections lead to bronchiolitis, which is swelling and inflammation of the small airways (bronchioles) in the lungs. Signs of bronchiolitis include:
- Rapid breathing or gasping for air
- Wheezing, crackling, or whistling sounds with breathing
- Retractions (sucking the chest inward) during breathing
- Cyanosis – blue-tinged lips or skin from lack of oxygen
Infants with bronchiolitis may need hospitalization for oxygen, fluids, or other respiratory support.
Pneumonia
In some cases, RSV can lead to pneumonia, a lung infection causing inflammation in the air sacs. Bacterial pneumonia can occur as a complication of the viral RSV infection.
Signs of RSV pneumonia include:
- High fever above 102°F
- Chills
- Cough producing yellow, rust, green, or blood-tinged mucus
- Fast, shallow breathing
- Chest pain with breathing or coughing
- Loss of appetite and dehydration
Pneumonia requires prompt medical treatment. RSV pneumonia in infants may require hospitalization.
Risk factors for severe RSV
RSV can lead to severe infection requiring hospitalization, especially for:
- Premature infants born before 35 weeks gestation
- Infants less than 6 months old
- Infants with chronic lung conditions like bronchopulmonary dysplasia (BPD)
- Infants with hemodynamically significant congenital heart disease
- Infants with weakened immune systems
Additional risk factors include:
- Exposure to tobacco smoke
- Attending daycare with other infants
- Having school-aged siblings
- Not breastfeeding
- Low birth weight
- neuromuscular disease
- Multiple birth pregnancy (twins, triplets)
RSV hospitalization rates are highest at ages 0 to 3 months. About 1-2% of infants born at term require hospitalization for RSV in the first year of life.
How is RSV diagnosed?
Doctors may suspect RSV based on symptoms during peak RSV season. Definitive diagnosis involves testing respiratory secretions for the presence of RSV virus. Diagnostic options include:
- Rapid antigen testing: Quick immunoassay detects RSV proteins in nasal or throat secretions within minutes.
- Molecular testing: Nucleic acid amplification tests (NAATs) like PCR detect RSV genetic material in a nasal swab or other respiratory specimen.
- Viral culture: Taking a nasal swab specimen and allowing viruses present to grow in a lab setting for 1 to 10 days.
Molecular tests like PCR are considered the most accurate option for RSV diagnosis. Chest X-ray and complete blood count may also be done to assess disease severity and complications like pneumonia.
RSV treatment
There are no medications that specifically target and treat RSV since antibiotics only work on bacterial infections. Treatment focuses on relieving symptoms and preventing complications:
- Oxygen: Given for low blood oxygen levels seen with bronchiolitis or pneumonia.
- Fluids: Given intravenously to ensure adequate hydration.
- Suctioning: Using a bulb syringe to remove thick mucus from nose and mouth.
- Bronchodilators: Albuterol and epinephrine may provide some relief for wheezing.
The antiviral medication ribavirin may be used in some severe cases, but is not commonly given due to limited effectiveness and side effects. Those with severe disease may need time on a ventilator.
Most infants recover fully from RSV with supportive care to keep respiratory function stable while the infection runs its course. Call a doctor immediately if symptoms suddenly worsen or if a high fever persists for over 3 days which could signal bacterial infection.
Preventing RSV infection
Good hygiene like handwashing, avoiding sick contacts, and disinfecting surfaces can help lower RSV transmission. High risk infants may receive monthly RSV immunoglobulin injections or the RSV monoclonal antibody palivizumab during RSV season for passive immunization.
An RSV vaccine is not yet available, but several promising candidates are in development including mRNA vaccines similar to those used against COVID-19. Vaccinating pregnant women could confer protective RSV antibodies to developing babies.
Conclusion
RSV is a common respiratory virus that usually causes mild cold-like symptoms but can be severe, especially for young infants and those with compromised immune systems or lung conditions. RSV spreads through respiratory droplets and progresses after a 4-6 day incubation period.
Early symptoms resemble a cold, but can rapidly advance to lower respiratory tract infection leading to bronchiolitis and pneumonia in severe cases. RSV can be diagnosed through rapid antigen testing, molecular assays, or viral culture.
Treatment focuses on respiratory support and relieving symptoms while the infection runs its course. RSV can be life-threatening in high-risk infants who may require hospitalization. Preventive strategies include good hygiene, avoiding exposure, and prophylaxis injections for those at highest risk. Research is ongoing to develop a safe and effective RSV vaccine.