Viruses

• According to the Mayo Clinic, many acute bronchitis cases are caused by the same viruses that infect people with the common cold.
  
  

Stomach Acid

• Individuals with gastroesophageal reflux disease may have stomach acid back up into their upper airway and cause inflammation to occur.
  
  

Environment

• Chronic bronchitis can develop after exposure to air pollutants, dusts and fumes. Occupational bronchitis can occur when an employee is exposed to chemicals and toxins that harm the lungs.
  
  

Smoking

• Cigarette smoking is the leading cause of chronic bronchitis and a major cause of acute bronchitis. Long-term exposure to second hand smoke can raise a person's risk of chronic bronchitis.
  
  

Low Resistance

• Older adults, young children and people with weakened immune systems have a decreased resistance to bronchitis infections.
  
  

Prevention

• Individuals can lower their risk of developing bronchitis by avoiding cigarette smoke, reducing exposure to people with infectious disease and regular hand washing.