Common<unk>  of<unk>  bronchitis include viruses, bacteria and environmental factors. Among these<unk> , influenza virus is the most common<unk>  especially during the winter.
Acute bronchitis causes
Chronic bronchitis causes
Bronchitis causes
Bronchiectasis causes
Bronchiolitis causes
Lipoid pneumonia causes
Eosinophilic pneumonia causes
Pneumoconiosis causes