Bronchiolitis is an infection of the small airways of the lower lungs.

In This Article, We’ll Discuss:

What Causes Bronchiolitis?

Although several viruses can cause bronchiolitis, the most common (and infamous) culprit is RSV (the Respiratory Syncytial Virus).

When is RSV Bronchiolitis Most Prevalent and How Does it Spread?

“RSV Bronchiolitis” (bronchiolitis caused by RSV) is most commonly seen in the fall through late spring (September through May) in kids under 2 years of age. It’s spread by touching surfaces with the virus on them and through close contact with mouth or nose secretions (think: spit and snot).

Why Do Doctors Worry About Bronchiolitis?

Docs worry about bronchiolitis because it can cause major breathing problems in children, especially in premature babies and infants with lung disease or heart problems.

Signs of Bronchiolitis Include the Following:

  • Cold-Like Symptoms: A runny nose and a cough.
  • Wheezing (in Some Kids).
  • Trouble Breathing

    Signs of Respiratory Distress Include:
    • Breathing fast.
    • Nasal flaring (when the nostrils go in and out).
    • Retractions (when the spaces between the ribs get sucked in with each breath).
    • Grunting noises at the end of each breath. 
    • Head bobbing (i.e. when a baby’s head moves up and down with each breath because they’re using their neck muscles to help them breathe).
  • An Ear Infection: Kids with RSV bronchiolitis are at a higher risk of developing ear infections.1
  • Poor Feeding: Babies with bronchiolitis often “pop off” the breast or bottle when feeding.

    Why? Because they have trouble coordinating their feeding and breathing when they’re congested. This is especially true for babies under 2 months of age, who are “obligate nasal breathers” (meaning they tend to breathe through their noses, rather than through their mouths).

PediaTip: If your baby has bronchiolitis, feed them smaller amounts more frequently and take extra breaks during feeding to prevent themr from getting tuckered out. In addition, keep track of your little one’s wet diapers to make sure that they’re staying hydrated (FYI: they should have at least 3+ wet diapers per day). 

Insider Info:

  • RSV Bronchiolitis can be sneaky because the symptoms peak around Day 4 or 5 of the illness, whereas most colds peak around Day 2 or 3. So, just when you think you’re out of the woods with RSV, it gets worse. Thanks a lot RSV!
  • Studies show that children who have an RSV infection before age 1, are 2-4 times more likely to develop asthma down the road (vs. the general population).

How is Bronchiolitis Diagnosed?

  • The child’s symptoms will steer the doctor in the direction of a bronchiolitis diagnosis. 
  • If the doctor suspects bronchiolitis, they will test for RSV. The RSV test is a “rapid test” that can be done in the office. Results take about 10-15 minutes to come back. 

    Reality Check: The RSV rapid test is not the most fun test in the world to get. It involves sticking a big Q-tip deep into the baby’s nose.

    The Silver Lining: The discomfort doesn’t last long. 

    If the RSV test is positive, the doctor will want to watch the baby more closely because (as mentioned above) RSV bronchiolitis tends to get worse before it gets better.

How is Bronchiolitis (Both RSV Bronchiolitis and Bronchiolitis Caused by Other Viruses) Treated?

Because bronchiolitis is caused by a virus, doctors can’t treat it with antibiotics. Doctors, therefore, manage it with “supportive care,” meaning they wait it out while trying to keep the patient comfortable.

Supportive Care Includes:

  • Offering the baby plenty of fluids.
  • Slowing down their feeds.
  • Keeping an eye on their breathing. 
  • Using non-medicated saline nose drops to help with the congestion.

For More Severe Cases:

Babies with respiratory distress and/or poor feeding may need extra support in the hospital. In the hospital, doctors can give the baby supplemental (extra) oxygen and/or IV fluids. Some babies who wheeze with RSV bronchiolitis respond to asthma medications that help open up the airways (think: albuterol). The doctor may, therefore, do a “trial of albuterol” to see if it helps. 

Insider Info: In the hospital, the medical staff and parents of patients with RSV must wear “contact isolation” gowns and, at times, masks. Contact isolation gowns are disposable (often yellow) gowns that help prevent the spread of the infection to other people in the hospital. As mentioned above, RSV clings to surfaces and is transmitted through close contact with mouth and nose secretions. The medical staff doesn’t want the virus to cling to their clothes or post up in their noses before they go into another patient’s room. 

How Can RSV Be Prevented?

Back in the day, doctors didn’t have many tools in their arsenal to prevent RSV infections in babies. Fast forward to today and we now have 3 RSV-preventing tools at our disposal, two of which are fresh off the market. Here are the players…

1. Pfizer’s Abrysso Vaccine (the FIRST FDA-Approved Vaccine That Protects Newborns Against RSV).

One of the slightly confusing things about the Abrysso vaccine is that it’s administered to PREGNANT people (not to their babies).

How Does That Work?

Expectant moms receive the vaccine in their third trimester and this protects their newborn from RSV for the first 6 months of life.

In the News: The Abrysso vaccine has gotten some bad press because some experts think it could be linked to preterm birth.

Why are They Saying this? Because Pfizer’s phase 3 clinical trial found a preterm birth rate of 5.6% in the vaccine group vs. 4.7% in the placebo group.

As we often (frustratingly) see with medication & vaccine studies, it isn’t clear if the vaccine is TRULY causing preterm birth or if it’s an (unrelated) coincidence.

In the end, the FDA approved the vaccine, saying the difference between the vaccine group and the placebo group wasn’t “statistically significant” and that the benefits of the vaccine greatly outweigh its risks. Still, other experts are calling for more data. Therefore, I would recommend that you ask your OB/GYN for their guidance when it comes to this vaccine.

2. Beyfortus (a “Monoclonal Antibody Shot” That Was Approved in June 2023).

The FDA has also given the green light to Beyfortus, another RSV-fighting tool. Unlike Abrysso, Beyfortus is a “monoclonal antibody” shot (through which preformed antibodies against RSV are injected into the body). Although this monoclonal antibody shot isn’t technically a vaccine (because it works through a different mechanism), it still protects against RSV infections.

Beyfortus has been approved for ALL infants under 8 months of age and for some higher-risk children 9-18 months of age.

3. Synagis (a “Monoclonal Antibody Shot” That’s Been Around Since the 90s, But That Only Certain “High-Risk” Kids are Eligible For).

Synagis (fancy name: Palivizumab) was first approved by the FDA in 1998. Like Beyfortus, it’s a monoclonal antibody shot (not a vaccine). Unlike Beyfortus, it has to be given multiple times during RSV season and only certain high-risk kids are eligible for it.

These “High-Risk” Children Include:

1. Premature babies under 1 year of age who were born before 29 weeks,


2. Kids under 2 years with bad respiratory issues, cardiac issues, and/or severely weakened immune systems. 

Synagis is given every month during RSV season for a total of 5-6 doses. Remember, RSV seasons starts in the fall and goes into the spring (think: September to May).

Insider Info: Synagis is EXPENSIVE – it costs about $1000 a pop. This adds up to $5000-6000 per eligible child per RSV season. As you can imagine, getting insurance companies to cover such a hefty sum can feel like pulling teeth.

If your baby qualifies for Synagis, make sure that their primary care doctor, pulmonologist (lung doctor), or cardiologist (heart doctor) gets on it sooner rather than later. One of these doctors will need to submit the paperwork early in the fall (around September). You might want to start hounding your insurance company around this time, too. 

Weighing Your Child’s Options:

If you’re pregnant or you have a child under 2 years, talk to your OB/GYN or your child’s pediatrician about which type of RSV-prevention is best for your little one. Based on the current information, it seems that Beyfortus will probably replace Synagis because it’s more powerful, it can be given to a broader population (not just high-risk kids), and it lasts longer (meaning you only need 1 shot of it per season vs. the 5+ doses kids need with Synagis).

As for the Abrysso vaccine and the Beyfortus monoclonal antibody shot, it isn’t clear whether BOTH will be recommended for each eligible child or just one of the two. Giving both would be expensive, so it’s likely that just one will be recommended.

The Bottom Line

Bronchiolitis is a common respiratory illness in kids under 2 years. RSV bronchiolitis can be serious in young children (because their airways are so small), particularly in those who were born prematurely or who have an underlying lung or heart problem. As RSV season rolls around, ask your OB/GYN or the pediatrician what type of RSV prevention they recommend for your child based on their age and medical history. In addition, be on the lookout for signs of RSV bronchiolitis and don’t hesitate to call the doctor (or 911) if your child develops a cold that seems to be getting worse or that’s accompanied by trouble breathing.