Bronchiolitis incubation period: when symptoms may start

The time between exposure and the first signs is an estimate, because it varies with the virus and the child's immune response. A child can spread a respiratory virus before obvious breathing symptoms appear, so an exposure is not always easy to identify.

Incubation period means the interval between catching an infection and noticing its first symptoms. Bronchiolitis often starts like a common cold, with a runny or blocked nose, reduced feeding, and a cough. Breathing may become faster or noisier as inflammation and mucus affect the small airways.

Symptoms can change over the following days. A cough may become more persistent, and wheezing or chest pulling may develop. These features describe bronchiolitis in a child; they do not mean that every cough or wheeze is bronchiolitis. See [Bronchiolitis](/conditions/bronchiolitis/) for the wider condition overview.

Watch the child's breathing, alertness, temperature, and ability to drink. Offer smaller feeds more often if congestion makes feeding tiring, and keep the child away from cigarette smoke. Handwashing and avoiding close contact with vulnerable infants can reduce spread.

A blocked nose can make feeding harder, while coughing and wheezing can disturb sleep. Keep a simple record of when symptoms started and whether they are changing. You can learn more about [Cough](/symptoms/cough/) and [Wheezing](/symptoms/wheezing/) as symptoms to discuss with a clinician.

Arrange prompt medical assessment if the child is breathing faster than usual, working hard to breathe, taking much less fluid, or having fewer wet nappies. A clinician should also assess a young infant with a fever, a child who is unusually sleepy, or symptoms that are getting worse rather than settling.

Seek emergency help if the child has pauses in breathing, blue or grey lips, severe difficulty breathing, or cannot stay awake. Do not wait for the expected incubation period to finish when breathing or hydration is a concern. A [Child Health Consultation](/treatments/consultations-and-assessment/child-health-consultation/) can provide an examination and safety advice. [Fever](/symptoms/fever/) may be useful to review alongside other symptoms.

Ask which symptoms should trigger same-day review, how to judge whether feeding is adequate, and whether the child's age or medical history increases concern. Ask before using medicines for cough or breathing; treatment depends on the examination and the child's condition. [Nebuliser Treatment](/treatments/acute-and-urgent-care/nebuliser-treatment/) is one treatment topic your clinician can explain if it is relevant.