Is Bronchitis Contagious?
Yes, acute bronchitis is contagious because it is predominantly caused by respiratory viruses (>90% of cases) that spread from person to person through respiratory droplets. 1
Understanding the Contagious Nature
Acute Bronchitis Transmission
Viral etiology dominates: Respiratory viruses cause more than 90% of acute bronchitis cases, making it inherently contagious during the infectious period. 1, 2, 3
Common viral culprits include: 1
- Influenza A and B (highly contagious with rapid community spread)
- Respiratory syncytial virus (RSV) - particularly contagious in households with children and institutional settings, with attack rates of 61-75%
- Parainfluenza
- Coronavirus
- Rhinovirus
- Adenovirus
Transmission occurs through: 1
- Respiratory droplets from coughing and sneezing
- Direct contact with contaminated surfaces
- Close personal contact during the symptomatic period
Specific High-Risk Scenarios
Influenza-related bronchitis is particularly contagious when circulating in the community, with the presence of both cough and fever within 48 hours strongly predicting influenza infection. 1
RSV causes high attack rates (61-75%) in geriatric wards, senior day care settings, nursing homes, and households with small children. 1
Bacterial causes (Mycoplasma pneumoniae, Chlamydophila pneumoniae, Bordetella pertussis) account for only 5-10% of cases but are also contagious, with higher incidences during community outbreaks and in congregate settings like military barracks and college campuses. 1
Chronic Bronchitis: A Different Story
Chronic bronchitis itself is NOT contagious because it results from prolonged exposure to pulmonary irritants (primarily cigarette smoke and atmospheric pollution), not from infectious agents. 1
However, patients with chronic bronchitis frequently experience acute infectious exacerbations that ARE contagious, typically triggered by viral infections (approximately one-third of episodes) including rhinovirus, coronavirus, influenza B, and parainfluenza. 1
Clinical Implications for Contagion Period
Most contagious during active symptoms: The infectious period typically corresponds with the symptomatic phase, particularly when cough and respiratory symptoms are most prominent. 1
Duration of contagiousness: While acute bronchitis symptoms last approximately 2-3 weeks, the contagious period is generally shorter and corresponds to the active viral shedding phase (typically the first 5-7 days of illness). 2, 4
Important Caveats
SARS-CoV (historical context) represented a highly infectious cause of acute bronchitis-like illness, with 77% of Toronto outbreak patients exposed in hospital settings, highlighting the importance of infection control measures during novel respiratory pathogen outbreaks. 1
Pertussis (whooping cough) may account for up to 25% of adults with nonspecific lower respiratory symptoms and is highly contagious, particularly to unimmunized infants. 5