What are the typical causes of bronchitis (inflammation of the bronchial tubes)?

From the Guidelines

Bronchitis is typically caused by viral infections, with the common cold and influenza viruses being the most frequent culprits, as well as environmental irritants such as tobacco smoke and air pollution, as supported by the most recent evidence 1. The causes of bronchitis can be broken down into:

• Viral infections, including the common cold and influenza viruses, which are the most frequent causes of acute bronchitis 1
• Bacterial infections, which can also cause bronchitis, though less commonly 1
• Environmental irritants, including:
  • Tobacco smoke (both firsthand and secondhand) 1
  • Air pollution 1
  • Dust 1
  • Chemical fumes in workplaces 1 People with underlying conditions like asthma, allergies, or COPD have increased susceptibility to bronchitis 1.

Key Factors

The key factors that contribute to the development of bronchitis include:

• Long-term exposure to irritants, such as tobacco smoke and air pollution, which can lead to chronic bronchitis 1
• Underlying conditions, such as asthma, allergies, or COPD, which can increase susceptibility to bronchitis 1
• Weather changes and low humidity, which can exacerbate symptoms by further irritating the airways 1 The most important factor in preventing and treating bronchitis is to avoid exposure to irritants, such as tobacco smoke and air pollution, as recommended by the most recent evidence 1.

From the Research

Typical Causes of Bronchitis

The typical causes of bronchitis can be summarized as follows:

• Viral infections are responsible for more than 90 percent of acute bronchitis infections 2
• Bacterial infections can also cause bronchitis, but are less common 3, 4
• Environmental pollutants and allergic responses can contribute to the development of bronchitis 4
• Cigarette smoking is a major etiologic factor for chronic bronchitis 4
• Other potential causes of acute cough, including pertussis, COVID-19, influenza, and community-acquired pneumonia, should be considered in the differential diagnosis 3, 5

Risk Factors

Certain risk factors can increase the likelihood of developing bronchitis, including:

• Smoking 4
• Exposure to environmental tobacco smoke 6
• Age, with older adults being at increased risk of developing pneumonia 2, 5
• Underlying respiratory conditions, such as asthma or chronic obstructive pulmonary disease 3, 4

Infectious Agents

The infectious agents that can cause bronchitis include:

• Viruses, such as influenza and COVID-19 3, 2, 5
• Bacteria, such as those that cause pertussis and pneumonia 3, 2, 5