Bronchiolitis vs Pneumonia
Content reviewed against published AAP, CDC guidelines
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If your baby has been diagnosed with or you suspect bronchiolitis vs pneumonia, here is what the evidence says.
The short answer
Bronchiolitis and pneumonia are both lower respiratory infections in babies but affect different parts of the lungs. Bronchiolitis inflames the small airways (bronchioles) and is almost always caused by viruses like RSV, primarily affecting babies under 2. Pneumonia infects the air sacs (alveoli) and can be caused by viruses or bacteria. Both can cause coughing, fast breathing, and difficulty breathing, but their treatments differ -- bronchiolitis is managed with supportive care while bacterial pneumonia requires antibiotics.
Key takeaways
- Bronchiolitis and pneumonia are both lower respiratory infections in babies but affect different parts of the lungs. Bronchiolitis inflames the small airways (bronchioles) and is almost always caused by viruses like RSV, primarily affecting babies under 2. Pneumonia infects the air sacs (alveoli) and can be caused by viruses or bacteria. Both can cause coughing, fast breathing, and difficulty breathing, but their treatments differ -- bronchiolitis is managed with supportive care while bacterial pneumonia requires antibiotics.
- Usually normal when: Baby has a cold with mild cough and congestion but is breathing comfortably and feeding well
- Call your doctor if: Baby is breathing very fast (over 60 breaths per minute) or has visible chest retractions when calm
- Varies by age — see the age-by-age breakdown below
“Fever itself is not an illness — rather, it is a sign or symptom that the body is fighting an infection. Fever stimulates certain defenses, such as the white blood cells, which attack and destroy invading bacteria.”
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By Age
What to expect by age
0-3 months
Both bronchiolitis and pneumonia can be serious in very young infants. Bronchiolitis from RSV is the most common cause of hospitalization in this age group. Symptoms include runny nose progressing to cough, wheezing, and difficulty breathing over 3-5 days. Pneumonia in newborns may present with fewer obvious respiratory symptoms and more general signs like poor feeding, lethargy, and temperature instability. Any breathing difficulty in a baby under 3 months requires prompt medical evaluation.
3-6 months
Bronchiolitis typically starts as a cold with runny nose and cough, then progresses to wheezing and increased work of breathing around day 3-5 of illness. The illness peaks around day 5-7 and gradually improves over 2-3 weeks. Pneumonia may present similarly but often includes higher fever, more localized crackles heard by the doctor, and may not improve on the expected bronchiolitis timeline. Your doctor can distinguish between them through examination and sometimes a chest X-ray.
6-12 months
Bronchiolitis remains common in this age group during fall and winter months. If your baby seems to be getting worse after day 5-7 of illness, develops a new fever after initially improving, or looks sicker than expected for bronchiolitis, pneumonia may be developing. Sometimes pneumonia occurs as a secondary bacterial infection after viral bronchiolitis. Trust your instincts -- if your baby seems more unwell than a typical cold, seek medical evaluation.
12 months+
Bronchiolitis becomes less common after age 2 as airways grow larger. Toddlers are more likely to develop pneumonia, which can be viral or bacterial. Bacterial pneumonia often causes higher persistent fevers, can appear suddenly, and may present with a child looking quite ill. Viral pneumonia tends to develop more gradually alongside other cold symptoms. Your pediatrician will determine the cause and whether antibiotics are needed.
What Should You Do?
When to take action
- Baby has a cold with mild cough and congestion but is breathing comfortably and feeding well
- Baby with bronchiolitis is on day 7-10 and symptoms are gradually improving
- Baby has a mild fever with cold symptoms but is alert, playing, and making wet diapers
- Baby's breathing rate is normal for age when calm and at rest
- Baby's cold seems to be getting worse rather than better after 5-7 days
- Baby develops a new fever after seeming to improve from a respiratory illness
- Baby is feeding less than 50% of normal or has noticeably fewer wet diapers
- Baby is breathing very fast (over 60 breaths per minute) or has visible chest retractions when calm
- Baby has bluish lips, extreme lethargy, or is not waking for feeds -- call 911 or go to the ER immediately
Doctor Visit Checklist
Bring this checklist to your next pediatrician visit to discuss Bronchiolitis vs Pneumonia.
Things to mention
- Baby's cold seems to be getting worse rather than better after 5-7 days
- Baby develops a new fever after seeming to improve from a respiratory illness
- Baby is feeding less than 50% of normal or has noticeably fewer wet diapers
Observations to share
- Baby's cold seems to be getting worse rather than better after 5-7 days
- Baby develops a new fever after seeming to improve from a respiratory illness
- Baby is feeding less than 50% of normal or has noticeably fewer wet diapers
Urgent signs to report immediately
- Baby is breathing very fast (over 60 breaths per minute) or has visible chest retractions when calm
- Baby has bluish lips, extreme lethargy, or is not waking for feeds -- call 911 or go to the ER immediately
My notes
From ismybabyalright.com — free, evidence-based baby health guides
Related Resources
Frequently asked questions
Is bronchiolitis vs pneumonia normal?
When should I call the doctor about bronchiolitis vs pneumonia?
When is bronchiolitis vs pneumonia normal?
What causes bronchiolitis vs pneumonia?
What should I mention to my pediatrician about bronchiolitis vs pneumonia?
Is bronchiolitis vs pneumonia normal at 0-3 months?
Is bronchiolitis vs pneumonia normal at 3-6 months?
Should I go to the ER for bronchiolitis vs pneumonia?
Does bronchiolitis vs pneumonia go away on its own?
References
All content follows our editorial policy and is reviewed against published clinical guidelines.
2,705 evidence-based guides6 authoritative medical sources
Related Resources
Bottom line
Most cases of bronchiolitis vs pneumonia are normal. Talk to your pediatrician if baby is breathing very fast (over 60 breaths per minute) or has visible chest retractions when calm.
Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.
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