What is RSV and how serious is it?

Respiratory Syncytial Virus (RSV) causes acute bronchiolitis, a lung infection affecting the smallest airways. Most children experience cold-like symptoms, but 1-2% require hospitalization for breathing support and hydration. RSV causes 58,000-80,000 hospitalizations annually in U.S. children under 5, with highest risk in infants under 6 months.

RSV spreads through respiratory droplets when infected people cough or sneeze, and by touching contaminated surfaces then touching the face. The virus can survive on hard surfaces for hours. It's highly contagious—outbreaks are common in daycare centers. People are typically contagious for 3-8 days, but infants and immunocompromised can spread it for 4 weeks.

What are warning signs that my baby needs medical care?

Seek immediate medical attention for: fast or difficult breathing, flaring nostrils, grunting with breathing, chest sinking in with each breath, bluish color around lips or fingernails, pauses in breathing (apnea), severe coughing or wheezing, refusal to breastfeed or drink, signs of dehydration (fewer wet diapers), or extreme irritability/lethargy.

Is there a vaccine or prevention for RSV?

Yes! New preventions available: 1) Maternal RSV vaccine (Abrysvo) given during pregnancy protects newborns. 2) Nirsevimab (Beyfortus) - monoclonal antibody injection for infants during first RSV season. 3) Palivizumab (Synagis) for high-risk infants. These have dramatically reduced hospitalizations since their 2023 introduction.

There's no specific antiviral treatment for RSV. Most cases are managed at home with supportive care: keep baby hydrated, use a cool-mist humidifier, suction nasal mucus, acetaminophen for fever (if over 3 months), and monitor breathing. Hospitalized infants may receive oxygen therapy, IV fluids, or breathing support. Antibiotics don't work because RSV is a virus.

When is RSV season and where is it active?

RSV season typically runs October through March in most U.S. regions, peaking in December-February. Southern states may see earlier starts. The virus can circulate year-round in some areas. Check the live outbreak data above for current RSV activity levels and geographic spread.

Acute Bronchiolitis (RSV)

1 Active Outbreak

Acute bronchiolitis is a common lung infection in young children and infants, most often caused by respiratory syncytial virus (RSV). It causes inflammation and congestion in the small airways of the lungs.

Countries Affected

Recent Cases (30d)

Active Outbreaks

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What is Acute Bronchiolitis (RSV)?

RSV is the leading cause of hospitalization in infants under one year old in the United States. Nearly all children get RSV by age 2, but it's most dangerous for premature babies, infants under 6 months, children with heart or lung conditions, and immunocompromised children. New preventive treatments are now available.

Symptoms

Runny nose and congestion
Cough (may be severe)
Rapid breathing or difficulty breathing
Wheezing (high-pitched whistling sound when breathing)
Fever (may be low-grade)
Decreased appetite and difficulty feeding
Irritability and restlessness
Apnea (pauses in breathing) in very young infants

Transmission

RSV spreads through respiratory droplets from coughing/sneezing and by touching contaminated surfaces (toys, doorknobs, counters). The virus can live on hard surfaces for many hours. Close contact in daycare, schools, and households facilitates spread.

Contagious Period: Typically 3-8 days; infants and immunocompromised people can be contagious for up to 4 weeks

Prevention

Maternal RSV vaccine (Abrysvo) during pregnancy (weeks 32-36)
Nirsevimab (Beyfortus) monoclonal antibody for infants
Palivizumab (Synagis) monthly injections for high-risk infants
Frequent handwashing with soap and water
Avoid touching face after touching contaminated surfaces
Keep babies away from sick people
Clean and disinfect toys and surfaces regularly
Avoid crowded places during RSV season with young infants
Don't smoke around children (increases RSV risk and severity)

Active Outbreaks & Recent Cases

Real-time intelligence from global health monitoring and AI-powered surveillance

Data sources: BEACON, ProMED, WHO, CDC, and 50+ national health agencies

✓ Live data updated in real-time from global health sources

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Moldova, Chișinău Municipality 2026-05-13

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Expert Resources & References

Trusted information from leading health organizations

CDC

Official guidance from the U.S. Centers for Disease Control and Prevention

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WHO

Global disease surveillance and guidelines from the World Health Organization

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Research

Latest peer-reviewed research and clinical studies

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Medically Reviewed Content

Disease information on Virus Watcher is reviewed by our Chief Epidemiologist, a former CDC lead analyst for FluSight forecasting. Outbreak data is aggregated from verified sources including BEACON, ProMED, WHO, CDC, and 50+ national health agencies. This information is for educational purposes and should not replace professional medical advice.

Last reviewed: 2026-06-03

Frequently Asked Questions

Common questions about Acute Bronchiolitis (RSV) answered by our epidemiology team

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