What is bronchiolitis and what causes it?

Bronchiolitis is an inflammation of the bronchioles (small airways in the lungs) that affects babies and children under 2 years. In 75% of cases, it is caused by respiratory syncytial virus (RSV). It is the leading cause of respiratory hospitalization in babies in Brazil.

Is bronchiolitis contagious?

Yes. RSV is transmitted through respiratory droplets (coughing, sneezing) and contact with contaminated surfaces. The virus can survive up to 6 hours on surfaces, which is why handwashing is so important.

What is the difference between bronchiolitis and bronchitis?

Bronchiolitis affects the bronchioles (smaller airways) and occurs mainly in children under 2, caused by viruses like RSV. Bronchitis affects the bronchi (larger airways) and is more common in older children and adults. Treatment differs for each condition.

Is RSV prevention available in Brazil?

Yes. Brazil now offers two RSV protection options through the public health system (SUS): nirsevimab (Beyfortus) for high-risk babies since February 2026, and the maternal vaccine Abrysvo for pregnant women since December 2025. Private clinics may offer nirsevimab to all babies regardless of risk level.

Who qualifies for nirsevimab through Brazil's public system?

Through SUS, nirsevimab is available for premature babies (under 37 weeks) and children under 2 with comorbidities: congenital heart disease, bronchopulmonary dysplasia, Down syndrome, cystic fibrosis, immunodeficiencies, and neuromuscular diseases. In private clinics, it can be given to all babies.

How can I prevent bronchiolitis without vaccination?

Key prevention measures include frequent handwashing, avoiding crowded places in the first months of life, exclusive breastfeeding until 6 months, not smoking near the baby, and keeping rooms well-ventilated. People with colds or flu should avoid close contact with babies.

Bronchiolitis in Babies: Symptoms, Treatment, and RSV Prevention in Brazil

Bronchiolitis is the leading cause of respiratory hospitalization in babies in Brazil. In 2025 alone, the public health system (SUS) recorded 36,218 hospitalizations in children under 2 due to severe acute respiratory infection caused by RSV. The good news? Brazil now offers two new prevention options: nirsevimab (Beyfortus) for high-risk babies and the maternal vaccine Abrysvo for pregnant women. If you are an expat family in São Paulo, this guide explains everything you need to know about recognizing symptoms, managing bronchiolitis at home, and understanding the new RSV prevention options available in Brazil.

What Is Bronchiolitis?

Bronchiolitis is an inflammation of the bronchioles — the smallest airways in the lungs. When the virus reaches these structures, they swell and produce excess mucus, blocking airflow. This causes the characteristic wheezing and difficulty breathing. Babies who have had bronchiolitis may be at higher risk of developing asthma later in childhood.

The main cause is respiratory syncytial virus (RSV), responsible for 75% of cases. Other viruses like rhinovirus, parainfluenza, and metapneumovirus can also cause bronchiolitis, but RSV is the most severe and common. For expat families in Brazil, understanding this condition is particularly important because the RSV season in São Paulo typically runs from March through August — the autumn and winter months.

Bronchiolitis in Brazil: Key Numbers (SUS 2025)

120,176

SARI cases reported

36.6%

caused by RSV

36,218

hospitalizations in children < 2 years

Pediatrician's Tip

Bronchiolitis peaks between 2 and 6 months of age and is most common during autumn and winter. Premature babies, babies with heart disease, or chronic lung conditions are at much higher risk of severe illness. If your baby is in this age range, talk to your pediatrician about prevention options. Also monitor your baby's sleep patterns — difficulty sleeping may be an early sign of respiratory distress.

Symptoms: How to Identify Bronchiolitis

Bronchiolitis typically begins looking like a common cold and progresses in two phases:

Phase 1: Cold-like Symptoms (Days 1-3)

• Runny nose (clear discharge)
• Sneezing
• Low-grade fever (37.5-38.5°C / 99.5-101.3°F)
• Mild cough

At this stage, many parents assume it is just a cold.

Phase 2: Respiratory Distress (Days 3-5)

• Intense, persistent cough
• Wheezing (audible whistling sound)
• Difficulty breathing — rapid breathing and visible effort
• Difficulty feeding — baby stops breastfeeding to breathe
• Irritability and trouble sleeping

If your baby shows these symptoms, seek pediatric evaluation.

GO TO THE ER IMMEDIATELY If:

Rapid breathing (over 60/min in babies under 2 months, over 50/min in 2-12 months)
Count breaths for one full minute while the baby is calm
Visible breathing effort
Ribs showing, chest indrawing below the neck, nasal flaring
Blue or purple lips or fingertips (cyanosis)
Indicates lack of oxygen — this is an emergency
Pauses in breathing (apnea) — especially in babies under 3 months
Baby stops breathing for several seconds
Feeding refusal (baby refuses to nurse or eat)
Intake less than half of normal amount
Signs of dehydration
Few wet diapers, dry mouth, crying without tears, sunken fontanelle

In São Paulo, Hospital Sabará (children-only), Hospital Albert Einstein, and Hospital Sírio-Libanês have well-equipped pediatric emergency departments. If you need help navigating the system, see our expat guide to pediatric care in Brazil.

Worried about your baby's breathing?

Dr. Paula is available via WhatsApp for quick assessments and can guide you on whether emergency care is needed.

Talk to the Pediatrician

Treatment: What to Do at Home

There is no specific antiviral treatment for bronchiolitis. Care focuses on supportive measures to help the baby breathe better and stay hydrated:

Recommended Home Care

Nasal saline washing
Before feedings and whenever the nose is blocked. Use saline drops or a gentle syringe.
Frequent hydration
Offer breast milk or formula more frequently in smaller amounts. Older babies: water and fluids.
Elevate the head of the crib
Place a rolled towel under the mattress to achieve a 30-degree angle. Never use a loose pillow.
Humidify the room
A humidifier or damp towel in the room helps thin secretions. This is especially helpful during São Paulo's dry winter months.

What NOT to Do

• Cough syrups — not recommended for babies and may mask symptoms
• Bronchodilators without prescription — nebulization with bronchodilators has no proven efficacy in bronchiolitis
• Antibiotics — bronchiolitis is viral; antibiotics do not help and may cause side effects
• Nasal decongestants — contraindicated in babies

When Is Hospitalization Needed?

Hospitalization is necessary when the baby needs supplemental oxygen, cannot feed adequately, experiences apnea, or has an oxygen saturation below 92%. Premature babies, those under 3 months, and babies with underlying conditions have earlier indications for hospitalization. Understanding the healthcare costs in São Paulo helps with financial planning.

RSV Prevention: New Options in Brazil (2025-2026)

Until recently, the only RSV immunization option was palivizumab (Synagis), reserved for very specific high-risk groups at a high cost. Now, Brazil has incorporated two new weapons against RSV into the national immunization program. For expat families, these options are available at both public and private healthcare facilities. Check our Brazilian vaccination guide for full details.

Nirsevimab (Beyfortus) — Direct Protection for Baby

• What it is: Monoclonal antibody (passive immunization, not a traditional vaccine) — a single dose protects for 5-6 months
• Available through SUS since: February 2026 (300,000 doses purchased)
• Who qualifies (SUS):Premature babies (<37 weeks) and children <2 years with comorbidities (heart disease, bronchopulmonary dysplasia, Down syndrome, cystic fibrosis, immunodeficiencies, neuromuscular diseases)
• Efficacy: 83.2% reduction in RSV hospitalizations (HARMONIE study, NEJM 2023) and 77.3% efficacy against medically-attended RSV infection (MELODY study, NEJM 2022)
• Private clinics: Nirsevimab may be available for all babies regardless of risk level — ask your pediatrician

Abrysvo — Maternal Vaccine (Mother Protects the Baby)

• What it is: Vaccine given to pregnant women from the 28th week of pregnancy — antibodies cross the placenta and protect the baby in the first months of life
• Available through SUS since: December 2025 (673,000 doses purchased)
• Who qualifies: All pregnant women, from the 28th week of pregnancy
• Efficacy: 81.8% against severe disease in the first 90 days of life and 69.4% in the first 180 days (MATISSE study, NEJM)
• Safety: No increase in serious adverse events for mother or baby in clinical trials

Comparison: Nirsevimab vs Abrysvo vs Palivizumab

Feature	Nirsevimab (Beyfortus)	Abrysvo (maternal)	Palivizumab (Synagis)
Type	Monoclonal antibody	Vaccine (recombinant protein)	Monoclonal antibody
Who receives it	Baby	Pregnant woman	Baby
Doses	1 dose	1 dose	5 monthly doses
Duration of protection	5-6 months	3-6 months (via placenta)	5 months (with 5 doses)
Efficacy	83% reduction in hospitalization	81.8% severe disease (90 days)	55% reduction in hospitalization
SUS availability	Since Feb/2026	Since Dec/2025	Restricted (high cost)

General Prevention Measures

Regardless of immunization status, these measures are fundamental to protect your baby:

Hygiene and Environment

• Handwashing — always before touching the baby
• Avoid crowded places in the first months of life
• Do not allow visits from people with colds
• Keep rooms well-ventilated
• Clean surfaces and toys frequently

Protecting Your Baby

• Exclusive breastfeeding until 6 months
• No smoking near the baby (secondhand smoke is a risk factor)
• Delay daycare entry if possible in the first months
• Keep vaccinations up to date
• If an adult has a cold or flu, wear a mask when caring for the baby

For Expat Families

If you are expecting a baby in Brazil, ask your obstetrician about the Abrysvo maternal vaccine from the 28th week. If your baby was born premature or has any of the high-risk conditions listed above, your pediatrician can help arrange nirsevimab through SUS or a private clinic. Both options are also available through private vaccination clinics for broader eligibility. Your international health insurance may reimburse these costs — ask for documentation in English.

Scientific References

• Hammitt LL, et al. Nirsevimab for Prevention of RSV in Healthy Late-Preterm and Term Infants (MELODY). N Engl J Med. 2022;386(9):837-846.
• Moline HL, et al. Effectiveness of Nirsevimab Against RSV-Associated Hospitalisation (HARMONIE). N Engl J Med. 2023.
• Kampmann B, et al. Bivalent Prefusion F Vaccine in Pregnancy to Prevent RSV Illness in Infants (MATISSE). N Engl J Med. 2023;388(16):1451-1464.
• WHO/SAGE. Recommendations on RSV Immunization. May 2025.
• Brazilian Ministry of Health. Incorporation of nirsevimab into SUS. February 2026.
• Brazilian Ministry of Health. Incorporation of Abrysvo maternal vaccine into PNI. December 2025.

Last updated: March 18, 2026